XtraDB/InnoDB Server System Variables

See Server System Variables for a complete list of system variables and instructions on setting them.

have_innodb

• Description: If the server supports InnoDB tables, will be set to YES, otherwise will be set to NO. Removed in MariaDB 10.0 - SHOW ENGINES can be used instead.
• Scope: Global
• Dynamic: No
• Removed: MariaDB 10.0

---

ignore_builtin_innodb

• Description: In older versions of MariaDB, setting this to 1 resulted in the built in InnoDB storage engine to be ignored. From MariaDB 5.5, InnoDB is the default and is always present, so this variable is ignored and setting it results in a warning.
• Commandline: --ignore-builtin-innodb
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Deprecated: MariaDB/MySQL 5.5.22

---

innodb_adaptive_checkpoint

• Description: Replaced with innodb_adaptive_flushing_method. Controls adaptive checkpointing. InnoDB's fuzzy checkpointing can cause stalls, as many dirty blocks are flushed at once as the checkpoint age nears the maximum. Adaptive checkpointing aims for more consistent flushing, approximately modified age / maximum checkpoint age. Can result in larger transaction log files
  • reflex Similar to innodb_max_dirty_pages_pct flushing but flushes blocks constantly and contiguously based on the oldest modified age. If the age exceeds 1/2 of the maximum age capacity, flushing will be weak contiguous. If the age exceeds 3/4, flushing will be strong. Strength can be adjusted by the variable innodb_io_capacity.
  • estimate The default, and independent of innodb_io_capacity. If the oldest modified age exceeds 1/2 of the maximum age capacity, blocks will be flushed every second at a rate determined by the number of modified blocks, LSN progress speed and the average age of all modified blocks.
  • keep_average Attempts to keep the I/O rate constant by using a shorter loop cycle of one tenth of a second. Designed for SSD cards.
• Commandline: --innodb_adaptive_checkpoint=#
• Scope: Global
• Dynamic: Yes
• Data Type: string
• Default Value: estimate
• Valid Values: none or 0, reflex or 1, estimate or 2, keep_average or 3
• Introduced: XtraDB 5.1.54-12.5
• Removed: XtraDB 5.5 - replaced with innodb_adaptive_flushing_method

---

innodb_adaptive_flushing

• Description: If set to 1, the default, the server will dynamically adjust the flush rate of dirty pages in the InnoDB buffer pool. This assists to reduce brief bursts of I/O activity.
• Commandline: --innodb_adaptive_flushing=#
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: ON

---

innodb_adaptive_flushing_lwm

• Description: Adaptive flushing is enabled when this this low water mark percentage of the redo log capacity is reached.
• Commandline: --innodb_adaptive_flushing_lwm=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 10
• Range: 0 to 70
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_adaptive_flushing_method

• Description: Determines the method of flushing dirty blocks from the InnoDB buffer pool. If set to native or 0, the original InnoDB method is used. The maximum checkpoint age is determined by the total length of all transaction log files. When the checkpoint age reaches the maximum checkpoint age, blocks are flushed. This can cause lag if there are many updates per second and many blocks with an almost identical age need to be flushed. If set to estimate or 1, the default, the oldest modified age will be compared with the maximum age capacity. If it's more than 1/4 of this age, blocks are flushed every second. The number of blocks flushed is determined by the number of modified blocks, the LSN progress speed and the average age of all modified blocks. It's therefore independent of the innodb_io_capacity for the 1-second loop, but not entirely so for the 10-second loop. If set to keep_average or 2, designed specifically for SSD cards, a shorter loop cycle is used in an attempt to keep the I/O rate constant. Removed in MariaDB 10.0/XtraDB 5.6 and replaced with InnoDB flushing method from MySQL 5.6.
• Commandline: innodb-adaptive-flushing-method=value
• Scope: Global
• Dynamic: Yes
• Data Type: enumeration
• Default Value: estimate
• Valid Values: native or 0, estimate or 1, #keep_average or 2
• Introduced: XtraDB 5.5.8-20
• Removed: MariaDB 10.0/XtraDB 5.6 - replaced with InnoDB flushing method from MySQL 5.6

---

innodb_adaptive_hash_index

• Description: If set to 1, the default, the InnoDB hash index is enabled.
• Commandline: --innodb_adaptive_hash_index=#
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: ON

---

innodb_adaptive_hash_index_partitions

• Description: Specifies the number of partitions for use in adaptive searching. If set to 1, no extra partitions are created.
• Commandline: innodb-adaptive-hash-index-partitions=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 1
• Range - 32 bit: 1 to 32
• Range - 64 bit: 1 to 64
• Introduced: XtraDB 5.5.8-20.0

---

innodb_adaptive_max_sleep_delay

• Description: Maximum time in microseconds to automatically adjust the innodb_thread_sleep_delay value to, based on the workload. Useful in extremely busy systems with hundreds of thousands of simultaneous connections.
• Commandline: --innodb_adaptive_max_sleep_delay=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 150000
• Range: 0 to 1000000
• Introduced: MariaDB 10.0

---

innodb_additional_mem_pool_size

• Description: Size in bytes of the InnoDB memory pool used for storing information about internal data structures. Defaults to 8MB, if your application has many tables and a large structure, and this is exceeded, operating system memory will be allocated and warning messages written to the error log, in which case you should increase this value.
• Commandline: --innodb_additional_mem_pool_size=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 8388608
• Range: 2097152 to 4294967295

---

innodb_api_bk_commit_interval

• Description: Time in seconds between auto-commits for idle connections using the InnoDB memcached interface (not implemented in MariaDB).
• Commandline: --innodb_api_bk_commit_interval=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 5
• Range: 1 to 1073741824
• Introduced: MariaDB 10.0 / MySQL 5.6.7

---

innodb_api_disable_rowlock

• Description: For use with MySQL's memcached (not implemented in MariaDB)
• Commandline: --innodb_api_disable_rowlock=#
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 10.0 / MySQL 5.6.6

---

innodb_api_enable_binlog

• Description: For use with MySQL's memcached (not implemented in MariaDB)
• Commandline: --innodb_api_enable_binlog=#
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 10.0 / MySQL 5.6.6

---

innodb_api_enable_mdl

• Description: For use with MySQL's memcached (not implemented in MariaDB)
• Commandline: --innodb_api_enable_mdl=#
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 10.0 / MySQL 5.6.6

---

innodb_api_trx_level

• Description: For use with MySQL's memcached (not implemented in MariaDB)
• Commandline: --innodb_api_trx_level=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 0
• Introduced: MariaDB 10.0 / MySQL 5.6.6

---

innodb_auto_lru_dump

• Description: Renamed innodb_buffer_pool_restore_at_startup since XtraDB 5.5.10-20.1, which was in turn replaced by innodb_buffer_pool_load_at_startup in MariaDB 10.0.
• Removed: XtraDB 5.5.10-20.1

---

innodb_autoextend_increment

• Description: Size in MB to increment an auto-extending shared tablespace file when it becomes full. If innodb_file_per_table was set to 1, this setting does not apply to the resulting per-table tablespace files, which are automatically extended in their own way.
• Commandline: --innodb_autoextend_increment=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 8
• Range: 1 to 1000

---

innodb_autoinc_lock_mode

• Description: Locking mode used for generating auto-increment values. 0 is the traditional lock mode, 1 the consecutive, and 2 the interleaved. See AUTO_INCREMENT handling in XtraDB/InnoDB for more on the lock modes.
• Commandline: --innodb_autoinc_lock_mode=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 1
• Range: 0 to 2

---

innodb_blocking_buffer_pool_restore

• Description: If set to 1 (0 is default), XtraDB will wait until the LRU dump is completely restored upon restart before reporting back to the server that it has successfully started up.
• Commandline: innodb-blocking-buffer-pool-restore={1|2}
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Introduced: XtraDB 5.5.16-22.0

---

innodb_buffer_pool_dump_at_shutdown

• Description: Whether to record pages cached in the buffer pool on server shutdown, which reduces the length of the warmup the next time the server starts. The related innodb_buffer_pool_load_at_startup specifies whether the buffer pool is automatically warmed up at startup.
• Commandline: --innodb_buffer_pool_dump_at_shutdown=#
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 10.0

---

innodb_buffer_pool_dump_now

• Description: Immediately records pages stored in the buffer pool. The related innodb_buffer_pool_load_now does the reverse, and will immediately warm up the buffer pool.
• Commandline: --innodb_buffer_pool_dump_now=#
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 10.0

---

innodb_buffer_pool_filename

• Description: The file that holds the buffer pool list of page numbers set by innodb_buffer_pool_dump_at_shutdown and innodb_buffer_pool_dump_now.
• Commandline: --innodb_buffer_pool_filename=file
• Scope: Global
• Dynamic: Yes
• Data Type: string
• Default Value: ib_buffer_pool
• Introduced: MariaDB 10.0

---

innodb_buffer_pool_instances

• Description: If innodb_buffer_pool_size is set to more than 1GB, innodb_buffer_pool_instances divides the InnoDB buffer pool into this many instances. The default is 1, but for large systems with buffer pools of many gigabytes, many instances can help reduce contention concurrency. Each instance manages its own data structures and takes an equal portion of the total buffer pool size, so for example if innodb_buffer_pool_size is 4GB and innodb_buffer_pool_instances is set to 4, each instance will be 1GB. Each instance should ideally be at least 1GB in size.
• Commandline: --innodb_buffer_pool_instances=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value - <= MariaDB 10.0: 1
• Default Value - >= MariaDB 10.0: 8
• Introduced: MariaDB/MySQL 5.5.4

---

innodb_buffer_pool_load_abort

• Description: Aborts the process of restoring buffer pool contents started by innodb_buffer_pool_load_at_startup or #innodb_buffer_pool_load_now|innodb_buffer_pool_load_now]].
• Commandline: --innodb_buffer_pool_load_abort=#
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 10.0

---

innodb_buffer_pool_load_at_startup

• Description: Specifies whether the buffer pool is automatically warmed up when the server starts by loading the pages held earlier. The related innodb_buffer_pool_dump_at_shutdown specifies whether pages are saved at shutdown.
• Commandline: --innodb_buffer_pool_load_at_startup=#
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 10.0

---

innodb_buffer_pool_load_now

• Description: Immediately warms up the buffer pool by loading the stored data pages. The related innodb_buffer_pool_dump_now does the reverse, and immediately records pages stored in the buffer pool.
• Commandline: --innodb_buffer_pool_load_now=#
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 10.0

---

innodb_buffer_pool_populate

• Description: When set to 1 (0 is default), XtraDB will preallocate pages in the buffer pool on starting up so that NUMA allocation decisions are made while the buffer cache is still clean.
• Commandline: innodb-buffer-pool-populate={0|1}
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Introduced: XtraDB 5.5.28-29.1

---

innodb_buffer_pool_restore_at_startup

• Description: Time in seconds between automatic buffer pool dumps. If set to a non-zero value, XtraDB will also perform an automatic restore of the buffer pool at startup. If set to 0, automatic dumps are not performed, nor automatic restores on startup. Replaced by innodb_buffer_pool_load_at_startup in MariaDB 10.0.
• Commandline: innodb-buffer-pool-restore-at-startup
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 0
• Range - 32 bit: 0 to 4294967295
• Range - 64 bit: 0 to 18446744073709547520
• Introduced: XtraDB 5.5.10-20.1
• Removed: MariaDB 10.0/XtraDB 5.6 - replaced by innodb_buffer_pool_load_at_startup

---

innodb_buffer_pool_shm_checksum

• Description: Used with Percona's SHM buffer pool patch in XtraDB 5.5. Later deprecated in XtraDB 5.5, and removed in XtraDB 5.6.
• Commandline: innodb-buffer-pool-shm-checksum={0|1}
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: ON
• Introduced: XtraDB 5.5
• Deprecated: XtraDB 5.5.13-20.4
• Removed: MariaDB 10.0/XtraDB 5.6

---

innodb_buffer_pool_shm_key

• Description: Used with Percona's SHM buffer pool patch in XtraDB 5.5. Later deprecated in XtraDB 5.5, and removed in XtraDB 5.6.
• Commandline: innodb-buffer-pool-shm-key={0|1}
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: 0
• Introduced: XtraDB 5.5
• Deprecated: XtraDB 5.5.13-20.4
• Removed: MariaDB 10.0/XtraDB 5.6

---

innodb_buffer_pool_size

• Description: InnoDB buffer pool size in bytes. The primary value to adjust on a database server with entirely/primarily XtraDB/InnoDB tables, can be set up to 80% of the total memory in these environments. If set to 2 GB or more, you will probably want to adjust innodb_buffer_pool_instances as well. See the XtraDB/InnoDB Buffer Pool for more on setting this variable.
• Commandline: --innodb_buffer_pool_size=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 134217728 (128MB)
• Maximum Value - 32 bit: 4294967295 (2³²-1 or 4096MB)
• Maximum Value - 64 bit: 18446744073709551615 (2⁶⁴-1)

---

innodb_change_buffer_max_size

• Description: Maximum size of the XtraDB/InnoDB Change Buffer as a percentage of the total buffer pool. The default is 25%, and this can be increased up to 50% for servers with high write activity, and lowered down to 0 for servers used exclusively for reporting.
• Commandline: --innodb_change_buffer_max_size=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 25
• Range: 0 to 50
• Introduced: MariaDB 10.0

---

innodb_change_buffering

• Description: Sets how InnoDB change buffering is performed. See XtraDB/InnoDB Change Buffering for details on the settings.
• Commandline: --innodb_change_buffering=#
• Scope: Global
• Dynamic: Yes
• Data Type: enumeration
• Default Value - <= MariaDB/MySQL 5.5.3: inserts
• Default Value - >= MariaDB/MySQL 5.5.4: none
• Valid Values - <= MariaDB/MySQL 5.5.3: inserts, none
• Valid Values - >= MariaDB/MySQL 5.5.4: inserts, none, deletes, purges, changes, all

---

innodb_checkpoint_age_target

• Description: The maximum value of the checkpoint age. If set to 0, has no effect. Removed in MariaDB 10.0/XtraDB 5.6 and replaced with InnoDB flushing method from MySQL 5.6.
• Commandline: innodb-checkpoint-age-target=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 0
• Range: 0 upwards
• Removed: MariaDB 10.0/XtraDB 5.6 - replaced with InnoDB flushing method from MySQL 5.6.

---

innodb_checksum_algorithm

• Description: A replacement for InnoDB's innodb_checksums and XtraDB's innodb_fast_checksum, specifies how the InnoDB tablespace checksum is generated and verified.
  • innodb: Backwards compatible with earlier versions.
  • crc32: A newer, faster algorithm, but incompatible with earlier versions. Tablespace blocks will be converted to the new format over time, meaning that a mix of checksums may be present.
  • none: Writes a constant rather than calculate a checksum.
  • strict_*: The strict_* options are the same as the regular options, but InnoDB will halt if it comes across a mix of checksum values. These are faster, as both new and old checksum values are not required, but can only be used when setting up tablespaces for the first time.
• Commandline: --innodb_checksum_algorithm=#
• Scope: Global
• Dynamic: Yes
• Data Type: enumeration
• Default Value: innodb
• Valid Values: innodb, crc32, none, strict_innodb, strict_crc32, strict_none
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_checksums

• Description: By default, InnoDB performs checksum validation on all pages read from disk, which provides extra fault tolerance. You would usually want this set to 1 in production environments, although setting it to 0 can provide marginal performance improvements. Replaced by innodb_checksum_algorithm in MariaDB 10.0, and should be removed to avoid conflicts. ON is equivalent to --innodb_checksum_algorithm=innodb and OFF to --innodb_checksum_algorithm=none.
• Commandline: --innodb_checksums, --skip-innodb-checksums
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: ON
• Deprecated: MariaDB 10.0

---

innodb_cmp_per_index_enabled

• Description: If set to ON (OFF is default), per-index compression statistics are stored in the INFORMATION_SCHEMA.INNODB_CMP_PER_INDEX table. These are expensive to record, so this setting should only be changed with care, such as for performance tuning on development or slave servers.
• Commandline: --innodb_cmp_per_index_enabled=#
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 10.0

---

innodb_commit_concurrency

• Description: Limit to the number of transaction threads that can can commit simultaneously. 0, the default, imposes no limit. While you can change from one positive limit to another at runtime, you cannot set this variable to 0, or change it from 0, while the server is running.
• Commandline: --innodb_commit_concurrency=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 0
• Range: 0 to 1000

---

innodb_compression_failure_threshold_pct

• Description: Specifies the percentage cutoff for expensive compression failures during updates to a compressed table, after which free space is added to each new compressed page, dynamically adjusted up to the level set by innodb_compression_pad_pct_max. Zero disables checking of compression efficiency and adjusting padding.
• Commandline: --innodb_compression_failure_threshold_pct=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 5
• Range: 0 to 100
• Introduced: MariaDB 10.0

---

innodb_compression_level

• Description: The level of zlib compression, from 1 to 9, used with InnoDB compressed tables and indexes. 1 gives the best speed, 9 the best compression. Defaults to 6.
• Commandline: --innodb_compression_level=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 6
• Range: 0 to 9
• Introduced: MariaDB 10.0

---

innodb_compression_pad_pct_max

• Description: The maximum percentage of reserved free space within each compressed page. Reserved free space is used when the page's data is reorganized and might be recompressed. Only used when innodb_compression_failure_threshold_pct is not zero, and the rate of compression failures exceeds its setting.
• Commandline: --innodb_compression_pad_pct_max=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 50
• Range: 0 to 75
• Introduced: MariaDB 10.0

---

innodb_concurrency_tickets

• Description: Number of times a newly-entered thread can enter and leave InnoDB until it is again subject to the limitations of innodb_thread_concurrency and may possibly be queued.
• Commandline: --innodb_concurrency_tickets=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 500

---

innodb_corrupt_table_action

• Description: When set to assert, the default, XtraDB will intentionally crash the server when it detects corrupted data in a single-table tablespace, with an assertion failure. When set to warn, it will pass corruption as corrupt table instead of crashing, and disable all further I/O (except for deletion) on the table file. If set to salvage, read access is permitted, but corrupted pages are ignored. innodb_file_per_table must be enabled for this option. Previously named innodb_pass_corrupt_table.
• Commandline: innodb-corrupt-table-action=value
• Scope: Global
• Dynamic: Yes
• Data Type: enumeration
• Default Value: assert
• Valid Values: assert, warn, salvage
• Introduced: XtraDB 5.5.10-20.1

---

innodb_data_file_path

• Description: Individual InnoDB data files, paths and sizes. The value of innodb_data_home_dir is joined to each path specified by innodb_data_file_path to get the full directory path. If innodb_data_home_dir is an empty string, absolute paths can be specified here. A file size is specified with K for kilobytes, M for megabytes and G for gigabytes, and whether or not to autoextend the data file is also specified.
• Commandline: --innodb_data_file_path=name
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: ibdata1:10M:autoextend

---

innodb_data_home_dir

• Description: Directory path for all InnoDB data files in the shared tablespace (assuming innodb_file_per_table is not enabled). File-specific information can be added in innodb_data_file_path, as well as absolute paths if innodb_data_home_dir is set to an empty string.
• Commandline: --innodb_data_home_dir=path
• Scope: Global
• Dynamic: No
• Data Type: directory name
• Default Value: The MariaDB data directory

---

innodb_dict_size_limit

• Description: Size in bytes of a soft limit the memory used by tables in the data dictionary. Once this limit is reached, XtraDB will attempt to remove unused entries. If set to 0, the default and standard InnoDB behavior, there is no limit to memory usage. Removed in MariaDB 10.0/XtraDB 5.6 and replaced by MySQL 5.6's new table_definition_cache implementation.
• Commandline: innodb-dict-size-limit=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 0
• Default Value - 32 bit: 2147483648
• Default Value - 64 bit: 9223372036854775807
• Introduced: XtraDB 5.0.77-b13
• Removed: MariaDB 10.0/XtraDB 5.6 - replaced by MySQL 5.6's new table_definition_cache implementation.

---

innodb_disable_sort_file_cache

• Description: If set to 1 (0 is default), the operating system file system cache for merge-sort temporary files is disabled.
• Commandline: --innodb_disable_sort_file_cache=#
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_doublewrite

• Description: If set to 1, the default, to improve fault tolerance InnoDB first stores data to a doublewrite buffer before writing it to data file. Disabling will provide a marginal peformance improvement.
• Commandline: --innodb-doublewrite, --skip-innodb_doublewrite
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: ON

---

innodb_doublewrite_file

• Description: The absolute or relative path and filename to a dedicated tablespace for the doublewrite buffer. In heavy workloads, the doublewrite buffer can impact heavily on the server, and moving it to a different drive will reduce contention on random reads. Since the doublewrite buffer is mostly sequential writes, a traditional HDD is a better choice than SSD. This Percona XtraDB variable has not been ported to XtraDB 5.6.
• Commandline: innodb-doublewrite-file=filename
• Scope: Global
• Dynamic: No
• Data Type: filename
• Default Value: NULL
• Introduced: XtraDB 5.5.8-20.0
• Removed: MariaDB10.0/XtraDB 5.6

---

innodb_enable_unsafe_group_commit

• Description: Unneeded after XtraDB 1.0.5. If set to 0, the default, InnoDB will keep transactions between the transaction log and binary logs in the same order. Safer, but slower. If set to 1, transactions can be group-committed, but there is no guarantee of the order being kept, and a small risk of the two logs getting out of sync. In write-intensive environments, can lead to a significant improvement in performance.
• Commandline: --innodb-enable-unsafe-group-commit
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 0
• Range: 0 to 1
• Removed: Not needed after XtraDB 1.0.5

---

innodb_extra_rsegments

• Description: Removed in XtraDB 5.5. Usually there is one rollback segment protected by single mutex, a source of contention in high write environments. This option specifies a number of extra user rollback segments. Changing the default will make the data readable by XtraDB only, and is incompatible with InnoDB. After modifying, the server must be slow-shutdown. If there is existing data, it must be dumped before changing, and re-imported after the change has taken effect.
• Commandline: innodb-extra-rsegments
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 0
• Range: 0 to 126
• Introduced: XtraDB 5.1
• Removed: XtraDB 5.5

---

innodb_extra_undoslots

• Description: Usually, InnoDB has 1024 undo slots in its rollback segment, so 1024 transactions can run in parallel. New transactions will fail if all slots are used. Setting this variable to 1 expands the available undo slots to 4072. Not recommended unless you get the Warning: cannot find a free slot for an undo log error in the error log, as it makes data files unusable for ibbackup, or MariaDB servers not run with this option.
• Commandline: innodb-extra-undoslots
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Introduced: XtraDB 5.1

---

innodb_fake_changes

• Description: Enables the fake changes feature. In replication, setting up or restarting a slave can cause a replication reads to perform more slowly, as MariaDB is single-threaded and needs to read the data before it can execute the queries. This can be speeded up by prefetching threads to warm the server, replaying the statements and then rolling back at commit. This however has a overhead from locking rows only then to undo changes at rollback. Fake changes attempts to reduce this overhead by reading the rows for INSERT, UPDATE and DELETE statements but not updating them. The rollback is then very fast with little or nothing to do.
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: OFF
• Introduced: XtraDB 5.5.16-22.0

---

innodb_fast_checksum

• Description: Implements a more CPU efficient XtraDB checksum algorithm, useful for write-heavy loads with high I/O. If set to 1 on a server with tables that have been created with it set to 0, reads will be slower, so tables should be recreated (dumped and reloaded). XtraDB will fail to start if set to 0 and there are tables created while set to 1. Replaced with innodb_checksum_algorithm in MariaDB 10.0/XtraDB 5.6.
• Commandline: innodb-fast-checksum={0|1}
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Deprecated: XtraDB 5.5.28-29.2
• Removed: MariaDB 10.0/XtraDB 5.6 - replaced with innodb_checksum_algorithm

---

innodb_fast_shutdown

• Description: The shutdown mode. If set to 1, the default, InnoDB performs a fast shutdown, not performing a full purge or an insert buffer merge. If set to 0, InnoDB performs a slow shutdown, including full purge and insert buffer merge. If set to 2, the logs are flushed and a cold shutdown takes place, similar to a crash. The resulting startup then performs crash recovery. Mode 0 can be very slow, even taking hours in extreme cases, but is necessary if upgrading to a new major release. Mode 2 is extremely fast, in cases of emergency, but risks corruption.
• Commandline: --innodb_fast_shutdown[=#]
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 1
• Range: 0 to 2

---

innodb_file_format

• Description: File format for new InnoDB tables. Can either be Antelope, the default and the original format, or Barracuda, which supports compression. See XtraDB/InnoDB File Format for more on the file formats.
• Commandline: --innodb_file_format=#
• Scope: Global
• Dynamic: Yes
• Data Type: string
• Default Value: Antelope (MariaDB/MySQL >= 5.5.7), Barracuda (MariaDB/MySQL 5.5.0 to 5.5.6)
• Valid Values: Antelope, Barracuda

---

innodb_file_format_check

• Description: If set to 1, the default, InnoDB checks the shared tablespace file format tag. If this is higher than the current version supported by XtraDB/InnoDB (for example Barracuda when only Antelope is supported), XtraDB/InnoDB will will not start. If it the value is not higher, XtraDB/InnoDB starts correctly and the innodb_file_format_max value is set to this value. If innodb_file_format_check is set to 0, no checking is performed. See XtraDB/InnoDB File Format for more on the file formats.
• Commandline: --innodb_file_format_check=#
• Scope: Global
• Dynamic: No
• Data Type: boolean (>= MariaDB/MySQL 5.5.5)
• Default Value: ON (>= MariaDB/MySQL 5.5.5)

---

innodb_file_format_max

• Description: The highest XtraDB/InnoDB file format. This is set to the value of the file format tag in the shared tablespace on startup (see innodb_file_format_check. If the server later creates a higher table format, innodb_file_format_max is set to that value. See XtraDB/InnoDB File Format for more on the file formats.
• Commandline: --innodb_file_format_max=#
• Scope: Global
• Dynamic: Yes
• Data Type: string
• Default Value: Antelope
• Valid Values: Antelope, Barracuda
• Introduced: MariaDB/MySQL 5.5.5

---

innodb_file_per_table

• Description: If set to 1, new XtraDB/InnoDB tables are created with data and indexes stored in their own .ibd file. If set to 0, the default, new tables are created in the system tablespace. Compression is only available with per table storage.
• Commandline: --innodb_file_per_table
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: OFF (>= MariaDB/MySQL 5.5.7), ON (MariaDB/MySQL 5.5.0 to 5.5.6)

---

innodb_flush_log_at_timeout

• Description: Interval in seconds to write and flush the logs. Before MariaDB 10, this was fixed at one second, which is still the default, but this can now be changed. It's usually increased to reduce flushing and avoid impacting performance of binary log group commit.
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 1
• Range: 0 to 2700
• Introduced: MariaDB/MySQL 5.6

---

innodb_flush_log_at_trx_commit

• Description: If set to 1, the default, the log buffer is written to the log file and a flush to disk performed after each transaction. This is required for full ACID compliance. If set to 0, nothing is done on commit; rather the log buffer write and flush are performed once a second. This gives better performance, but a server crash can erase the last second of transactions. If set to 2, the log buffer is written after each commit, but flushing takes place once a second. Performance is slightly better, but a OS or power outage can cause the last second's transactions to be lost. Set to 1, along with sync_binlog=1 for the greatest level of fault tolerance. The value of innodb_use_global_flush_log_at_trx_commit determines whether this variable can be reset with a SET statement or not.
• Commandline: --innodb_flush_log_at_trx_commit[=#]
• Scope: Global
• Dynamic: Yes
• Data Type: enumeration
• Default Value: 1
• Valid Values: 0, 1, 2

---

innodb_flush_method

• Description: XtraDB/InnoDB flushing method. Windows always uses async_unbuffered and this variable then has no effect. On Unix, by default fsync() is used to flush data and logs. Adjusting this variable can give performance improvements, but behavior differs widely on different filesystems, and changing from the default has caused problems in some situations, so test and benchmark carefully before adjusting.
  • O_DSYNC - O_DSYNC is used to open and flush logs, and fsync() to flush the data files.
  • O_DIRECT - O_DIRECT or directio(), is used to open data files, and fsync() to flush data and logs.
  • fdatasync - an old default value that follows the default behavior of using fsync(), but replaced with the unset default to avoid confusion between fdatasync() and fysnc().
  • O_DIRECT_NO_FSYNC - introduced in MariaDB 10.0 / MySQL 5.6.7. Uses O_DIRECT during flushing I/O, but skips fsync() afterwards. Not suitable for XFS filesystems.
• Commandline: --innodb_flush_method=name
• Scope: Global
• Dynamic: No
• Data Type: enumeration
• Default Value: Not set.
• Valid Values: fdatasync, O_DSYNC, O_DIRECT, O_DIRECT_NO_FSYNC (MariaDB 10.0)

---

innodb_flush_neighbor_pages

• Description: Determines whether, when dirty pages are flushed to the data file, neighboring pages in the data file are flushed at the same time. If set to none, the feature is disabled. If set to area, the default, the standard InnoDB behavior is used. For each page to be flushed, dirty neighboring pages are flushed too. If there's little head seek delay, such as SSD or large enough write buffer, one of the other two options may be more efficient. If set to cont, for each page to be flushed, neighboring contiguous blocks are flushed at the same time. Being contiguous, a sequential I/O is used, unlike the random I/O used in area. Replaced by innodb_flush_neighbors in MariaDB 10.0/XtraDB 5.6.
• Commandline: innodb-flush-neighbor-pages=value
• Scope: Global
• Dynamic: Yes
• Data Type: enumeration
• Default Value: area
• Valid Values: none or 0, area or 1, cont or 2
• Removed: MariaDB 10.0/XtraDB 5.6 - replaced by innodb_flush_neighbors

---

innodb_flush_neighbors

• Description: Determines whether flushing a page from the buffer pool will flush other dirty pages in the same group of pages (extent). In high write environments, if flushing is not aggressive enough, it can fall behind resulting in higher memory usage, or if flushing is too aggressive, cause excess I/O activity. SSD devices, with low seek times, would be less likely to require dirty neighbor flushing to be set.
  • 1: The default, flushes contiguous dirty pages in the same extent from the buffer pool.
  • 0: No other dirty pages are flushed.
  • 2: Flushes dirty pages in the same extent from the buffer pool.
• Commandline: --innodb_flush_neighbors=#
• Scope: Global
• Dynamic: Yes
• Data Type: enumeration
• Default Value: 1
• Valid Values: 0, 1, 2
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_flushing_avg_loops

• Description: Determines how quickly adaptive flushing will respond to changing workloads. The value is the number of iterations that a previously calculated flushing state snapshot is kept. Increasing the value smooths and slows the rate that the flushing operations change, while decreasing it causes flushing activity to spike quickly in response to workload changes.
• Commandline: --innodb_flushing_avg_loops=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 30
• Range: 1 to 1000
• Introduced: MariaDB/MySQL 5.6

---

innodb_force_load_corrupted

• Description: Set to 0 by default, if set to 1, XtraDB/InnoDB will be permitted to load tables marked as corrupt. Only use this to recover data you can't recover any other way, or in troubleshooting. Always restore to 0 when the returning to regular use.
• Commandline: --innodb_force_load_corrupted
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB/MySQL 5.5.18

---

innodb_force_recovery

• Description: XtraDB/InnoDB crash recovery mode. 0 is the default. The other modes are for recovery purposes only, and no data can be changed while another mode is active. Some queries relying on indexes are also blocked. See XtraDB/InnoDB Recovery Modes for more on mode specifics.
• Commandline: --innodb_force_recovery=#
• Scope: Global
• Dynamic: No
• Data Type: enumeration
• Default Value: 0
• Range: 0 to 6

---

innodb_ft_aux_table

• Description: Diagnostic variable intended only to be set at runtime. It specifies the qualified name of an InnoDB table that has a FULLTEXT index, and after being set the INFORMATION_SCHEMA tables INNODB_FT_INDEX_TABLE, INNODB_FT_INDEX_CACHE, INNODB_FT_CONFIG, INNODB_FT_DELETED, and INNODB_FT_BEING_DELETED will contain search index information for the specified table.
• Commandline: --innodb_force_recovery=#
• Scope: Global
• Dynamic: Yes
• Data Type: string
• Default Value: 0
• Range: 0 to 6
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_ft_cache_size

• Description: Cache size available for a parsed document while creating an InnoDB FULLTEXT index.
• Commandline: --innodb_ft_cache_size=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 8000000
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_ft_enable_diag_print

• Description: If set to 1, additional full-text search diagnostic output is enabled.
• Commandline: --innodb_ft_enable_diag_print=#
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_ft_enable_stopword

• Description: If set to 1, the default, a set of stopwords is associated with an InnoDB FULLTEXT index when it is created. The stopword list comes from the table set by the innodb_ft_user_stopword_table, if set, otherwise the innodb_ft_server_stopword_table if that is set, or the built-in list if neither variable is set.
• Commandline: --innodb_ft_enable_stopword=#
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: ON
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_ft_max_token_size

• Description: Maximum length of words stored in an InnoDB FULLTEXT index. A larger limit will increase the size of the index, slowing down queries, but permit longer words to be searched for. In most normal situations, longer words are unlikely search terms.
• Commandline: --innodb_ft_max_token_size=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 84
• Range: 10 to 252
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_ft_min_token_size

• Description: Minimum length of words stored in an InnoDB FULLTEXT index. A smaller limit will increase the size of the index, slowing down queries, but permit shorter words to be searched for. For data stored in a Chinese, Japanese or Korean character set, a value of 1 should be specified to preserve functionality.
• Commandline: --innodb_ft_min_token_size=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 3
• Range: 0 to 16
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_ft_num_word_optimize

• Description: Number of words processed during each OPTIMIZE TABLE on an InnoDB FULLTEXT index. To ensure all changes are incorporated, multiple OPTIMIZE TABLE statements could be run in case of a substantial change to the index.
• Commandline: --innodb_ft_num_word_optimize=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 2000
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_ft_sort_pll_degree

• Description: Number of parallel threads used when building an InnoDB FULLTEXT index. See also innodb_sort_buffer_size.
• Commandline: --innodb_ft_sort_pll_degree=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 2
• Range: 1 to 32
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_ft_server_stopword_table

• Description: Table name containing a list of stopwords to ignore when creating an InnoDB FULLTEXT index, in the format db_name/table_name. The specified table must exist before this option is set, and must be an InnoDB table with a single column, a VARCHAR named VALUE.
• Commandline: --innodb_ft_server_stopword_table=db_name/table_name
• Scope: Global
• Dynamic: Yes
• Data Type: string
• Default Value: Empty
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_ft_user_stopword_table

• Description: Table name containing a list of stopwords to ignore when creating an InnoDB FULLTEXT index, in the format db_name/table_name. The specified table must exist before this option is set, and must be an InnoDB table with a single column, a VARCHAR named VALUE.
• Commandline: --innodb_ft_user_stopword_table=db_name/table_name
• Scope: Session
• Dynamic: Yes
• Data Type: string
• Default Value: Empty
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_ibuf_accel_rate

• Description: Allows the insert buffer activity to be adjusted. The following formula is used: [real activity] = [default activity] * (innodb_io_capacity/100) * (innodb_ibuf_accel_rate/100). As innodb_ibuf_accel_rate is increased from its default value of 100, the lowest setting, insert buffer activity is increased. See also innodb_io_capacity. This Percona XtraDB variable has not been ported to XtraDB 5.6.
• Commandline: innodb-ibuf-accel-rate=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 100
• Range: 100 to 999999999
• Introduced: XtraDB 5.5.8-20.0
• Removed: MariaDB 10.0/XtraDB 5.6

---

innodb_ibuf_active_contract

• Description: Specifies whether the insert buffer can be processed before it's full. If set to 0, the standard InnoDB method is used, and the buffer is not processed until it's full. If set to 1, the default, the insert buffer can be processed before it is full. This Percona XtraDB variable has not been ported to XtraDB 5.6.
• Commandline: innodb-ibuf-active-contract=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 1
• Range: 0 to 1
• Introduced: XtraDB 5.5.8-20.0
• Removed: MariaDB 10.0/XtraDB 5.6

---

innodb_ibuf_max_size

• Description: Maximum size in bytes of the insert buffer. Defaults to half the size of the buffer pool so you may want to reduce if you have a very large buffer pool. If set to 0, the insert buffer is disabled, which will cause all secondary index updates to be performed synchronously, usually at a cost to performance. This Percona XtraDB variable has not been ported to XtraDB 5.6.
• Commandline: innodb-ibuf-max-size=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 1/2 the size of the InnoDB buffer pool
• Range: 0 to 1/2 the size of the InnoDB buffer pool
• Removed: MariaDB 10.0/XtraDB 5.6

---

innodb_import_table_from_xtrabackup

• Description: If set to 1, permits importing of .ibd files exported with the XtraBackup --export option. Previously named innodb_expand_import. Removed in MariaDB 10.0/XtraDB 5.6 and replaced with MySQL 5.6's transportable tablespaces.
• Commandline: innodb-import-table-from-xtrabackup=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 0
• Range: 0 to 1
• Introduced: XtraDB 5.5.10-20.1
• Removed: MariaDB 10.0/XtraDB 5.6

---

innodb_io_capacity

• Description: Limit on I/O activity for XtraDB/InnoDB background tasks, including merging data from the insert buffer and flushing pages. Should be set to around the number of I/O operations per second that system can handle, based on the type of drive/s being used. You can also set it higher when the server starts to help with the extra workload at that time, and then reduce for normal use. Ideally, opt for a lower setting, as at higher value data is removed from the buffers too quickly, reducing the effectiveness of caching.
• Commandline: --innodb_io_capacity=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 200
• Range - 32 bit: 100 to 4294967295 (2³²-1 or 4096MB)
• Range - 64 bit: 100 to 18446744073709551615 (2⁶⁴-1)

---

innodb_io_capacity_max

• Description: Upper limit to which InnodDB can extend innodb_io_capacity in case of emergency. Only applicable if no value was specified for innodb_io_capacity when the server started up.
• Commandline: --innodb_io_capacity_max=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 200
• Range - 32 bit: 2000 to 4294967295 (2³²-1 or 4096MB)
• Range - 64 bit: 2000 to 18446744073709551615 (2⁶⁴-1)
• Introduced: MariaDB 10.0 / MySQL 5.6.6

---

innodb_kill_idle_transaction

• Description: Time in seconds before killing an idle XtraDB transaction. If set to 0 (the default), the feature is disabled. Used to prevent accidental user locks.
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 0
• Range: to
• Introduced: XtraDB 5.5.16-22.0

---

innodb_large_prefix

• Description: If set to 1, tables that use dynamic and compressed row formats (which require innodb_file_format to be barracuda and innodb_file_per_table to be true) are permitted to have index key prefixes up to 3072 bytes.
• Commandline: --innodb_large_prefix
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB/MySQL 5.5.14

---

innodb_lazy_drop_table

• Description: Deprecated and removed in XtraDB 5.6. DROP TABLE processing can take a long time when innodb_file_per_table is set to 1 and there's a large buffer pool. If innodb_lazy_drop_table is set to 1 (0 is default), XtraDB attempts to optimize DROP TABLE processing by deferring the dropping of related pages from the buffer pool until there is time, only initially marking them.
• Commandline: innodb-lazy-drop-table={0|1}
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: #0#
• Introduced: XtraDB 5.5.10-20.1
• Deprecated: XtraDB 5.5.30-30.2
• Removed: MariaDB 10.0/XtraDB 5.6

---

innodb_lock_wait_timeout

• Description: Time in seconds that an InnoDB transaction waits for an InnoDB row lock (not table lock) before giving up with the error ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction. When this occurs, the statement (not transaction) is rolled back. The whole transaction can be rolled back if the innodb_rollback_on_timeout option is used. Increase this for data warehousing applications or where other long-running operations are common, or decrease for OLTP and other highly interactive applications. This setting does not apply to deadlocks, which InnoDB detects immediately, rolling back a deadlocked transaction.
• Commandline: --innodb_lock_wait_timeout=#
• Scope: Global, Session
• Dynamic: Yes
• Data Type: numeric
• Default Value: 50
• Range: 1 to 1073741824

---

innodb_locking_fake_changes

• Description: If set to OFF, fake transactions (see innodb_fake_changes) don't take row locks. This is an experimental feature to attempt to deal with drawbacks in fake changes blocking real locks. It is not safe for use in all environments.
• Commandline: --innodb_locking_fake_changes
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: ON
• Introduced: XtraDB 5.5.28-29.2

---

innodb_locks_unsafe_for_binlog

• Description: Set to 0 by default, in which case XtraDB/InnoDB uses gap locking. If set to 1, gap locking is disabled for searches and index scans.
• Commandline: --innodb_locks_unsafe_for_binlog
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF

---

innodb_log_block_size

• Description: Size in bytes of the transaction log records. Generally 512, the default, or 4096, for SSD cards, are the only two useful values. If the server is restarted and this value is changed, all old log files need to be removed.
• Commandline: innodb-log-block-size=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 512
• Introduced: XtraDB 5.5

---

innodb_log_buffer_size

• Description: Size in bytes of the buffer for writing XtraDB/InnoDB log files to disk. Increasing this means larger transactions can run without needing to perform disk I/O before committing.
• Commandline: --innodb_log_buffer_size=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 8388608 (8MB)
• Range: 262144 to 4294967295 (256KB to 4096MB)

---

innodb_log_file_size

• Description: Size in bytes of each log file in the log group. The combined size can be no more than 4GB. Larger values mean less disk I/O due to less flushing checkpoint activity, but also slower recovery from a crash.
• Commandline: --innodb_log_file_size=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 5242880 (5MB)
• Range: 108576 to 4294967295 (106KB to 4096MB)

---

innodb_log_files_in_group

• Description: Number of log log files in the log group.
• Commandline: --innodb_log_files_in_group=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 2
• Range: 2 to 100

---

innodb_log_group_home_dir

• Description: Path to the XtraDB/InnoDB redo log files. If none is specified, files named ib_logfile0 and ib_logfile1, with a size of innodb_log_file_size are created in the data directory.
• Commandline: --innodb_log_group_home_dir=path
• Scope: Global
• Dynamic: No
• Data Type: directory name

---

innodb_lru_scan_depth

• Description: Specifies how far down the buffer pool LRU list the cleaning thread should look for dirty pages to flush. This process is performed once a second. In an I/O intensive-workload, can be increased if there is spare I/O capacity, or decreased if in a write-intensive workload with little spare I/O capacity.
• Commandline: --innodb_lru_scan_depth=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 1024
• Range - 32bit: 100 to 232-1
• Range - 64bit: 100 to 264-1
• Introduced: XtraDB 5.1.66-14.2

---

innodb_max_bitmap_file_size

• Description: Limit in bytes of the changed page bitmap files. For faster incremental backup with Xtrabackup, XtraDB tracks pages with changes written to them according to the redo log and writes the information to special changed page bitmap files. These files are rotated when the server restarts or when this limit is reached. See also innodb_track_changed_pages and innodb_max_changed_pages.
• Commandline: innodb-max-bitmap-file-size=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 4096 (4KB)
• Range: 4096 (4KB) to 18446744073709551615 (16EB)
• Introduced: XtraDB 5.1.66-14.2

---

innodb_max_changed_pages

• Description: Limit to the number of changed page bitmap files. See innodb_max_bitmap_file_size and innodb_track_changed_pages. Previously named innodb_changed_pages_limit
• Commandline: innodb-max-changed-pages=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 1000000
• Range: 1 upwards
• Introduced: XtraDB 5.1.67-14.4

---

innodb_max_dirty_pages_pct

• Description: Maximum percentage of unwritten (dirty) pages in the buffer pool.
• Commandline: --innodb_max_dirty_pages_pct=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 75
• Range: 0 to 99

---

innodb_max_dirty_pages_pct_lwm

• Description: Low water mark percentage of dirty pages that will enable preflushing to lower the dirty page ratio. If set to 0, the default, preflushing is disabled.
• Commandline: --innodb_max_dirty_pages_pct_lwm=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 0
• Range: 0 to 99
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_max_purge_lag

• Description: When purge operations are lagging on a busy server, setting innodb_max_purge_lag can help. By default set to 0, no lag, the figure is used to calculate a time lag for each INSERT, UPDATE, and DELETE when the system is lagging. XtraDB/InnoDB keeps a list of transactions with delete-marked index records due to UPDATE and DELETE statements. The length of this list is purge_lag, and the calculation, performed every ten seconds, is as follows: ((purge_lag/innodb_max_purge_lag)×10)–5 milliseconds.
• Commandline: --innodb_max_purge_lag=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 0
• Range: 0 to 4294967295

---

innodb_max_purge_lag_delay

• Description: Maximum delay in milliseconds imposed by the innodb_max_purge_lag setting. If set to 0, the default, there is no maximum.
• Commandline: --innodb_max_purge_lag_delay=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 0
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_merge_sort_block_size

• Description: Size in bytes of the block used for merge sorting in fast index creation. Replaced in MariaDB 10.0/XtraDB 5.6 by innodb_sort_buffer_size.
• Commandline: innodb-merge-sort-block-size=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 1048576 (1M)
• Range: 1048576 (1M) to 1073741824 (1G)
• Introduced: XtraDB 5.5.27-28.0
• Removed: MariaDB 10.0/XtraDB 5.6 - replaced by innodb_sort_buffer_size

---

innodb_mirrored_log_groups

• Description: Unused

---

innodb_monitor_disable

• Description: Disables the specified counters in the INFORMATION_SCHEMA.INNODB_METRICS table.
• Commandline: --innodb_monitor_disable=string
• Scope: Global
• Dynamic: Yes
• Data Type: string
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_monitor_enable

• Description: Enables the specified counters in the INFORMATION_SCHEMA.INNODB_METRICS table.
• Commandline: --innodb_monitor_enable=string
• Scope: Global
• Dynamic: Yes
• Data Type: string
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_monitor_reset

• Description: Resets the count value of the specified counters in the INFORMATION_SCHEMA.INNODB_METRICS table to zero.
• Commandline: --innodb_monitor_reset=string
• Scope: Global
• Dynamic: Yes
• Data Type: string
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_monitor_reset_all

• Description: Resets all values for the specified counters in the INFORMATION_SCHEMA.INNODB_METRICS table.
• Commandline: ---innodb_monitor_reset_all=string
• Scope: Global
• Dynamic: Yes
• Data Type: string
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_old_blocks_pct

• Description: Percentage of the buffer pool to use for the old block sublist.
• Commandline: --innodb_old_blocks_pct=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 37
• Range: 5 to 95

---

innodb_old_blocks_time

• Description: Time in milliseconds an inserted block must stay in the old sublist after its first access before it can be moved to the new sublist. '0' means "no delay". Setting a non-zero value can help prevent full table scans clogging the buffer pool. See also innodb_old_blocks_pct.
• Commandline: --innodb_old_blocks_time=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 0
• Range: 0 to 232-1

---

innodb_online_alter_log_max_size

• Description: The maximum size for temporary log files during online DDL (data and index structure changes). The temporary log file is used for each table being altered, or index being created, to store data changes to the table while the process is underway. The table is extended by innodb_sort_buffer_size up to the limit set by this variable. If this limit is exceeded, the online DDL operation fails and all uncommitted changes are rolled back. A lower value reduces the time a table could lock at the end of the operation to apply all the log's changes, but also increases the chance of the online DDL changes failing.
• Commandline: --innodb_online_alter_log_max_size=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 134217728
• Range: 65536 to 264-1
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_open_files

• Description: Maximum .ibd files MariaDB can have open at the same time. Only applies to systems with multiple XtraDB/InnoDB tablespaces, and is separate to the table cache and open_files_limit.
• Commandline: --innodb_open_files=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 300
• Range: 10 to 4294967295

---

innodb_optimize_fulltext_only

• Description: When set to 1 (0 is default), OPTIMIZE TABLE will only process InnoDB FULLTEXT index data. Only intended for use during fulltext index maintenance.
• Commandline: --innodb_optimize_fulltext_only=#
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_page_size

• Description: Size in bytes of the page size for all XtraDB/InnoDB tablespaces. The default, 16k, is suitable for most uses, but smaller page size might work more effectively in a situation with many small writes (OLTP), or with SSD storage, which usually has smaller block sizes. The page size is set when a MariaDB instance starts, and it remains constant afterwards. Note that Percona previously implemented its own experimental version of innodb_page_size, which was deprecated in XtraDB 5.5.30-30.2, and replaced in XtraDB 5.6 with the MySQL 5.6 version.
• Commandline: --innodb_page_size=#
• Scope: Global
• Dynamic: No
• Data Type: enumeration
• Default Value: 16384
• Valid Values: 4k OR 4096, 8k or 8192, 16k or 16384
• Introduced: XtraDB 5.5 and MySQL 5.6

---

innodb_print_all_deadlocks

• Description: If set to 1 (0 is default), all XtraDB/InnoDB transaction deadlock information is written to the error log.
• Commandline: --innodb_print_all_deadlocks=#
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB/MySQL 5.5.30

---

innodb_purge_batch_size

• Description: Units of redo log records that will trigger a purge operation. Together with innodb_purge_threads has a small effect on tuning.
• Commandline: --innodb_purge_batch_size=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 20
• Range: 2 to 5000
• Introduced: MariaDB/MySQL 5.5.4

---

innodb_purge_threads

• Description: Number of threads dedicated to XtraDB purge operations. If set to 0, the default, purging is done with the master thread. If set to 1, the current maximum, purging is done on a separate thread with could reduce contention. Currently has minimal effect, but is a future area of improvement. See also innodb_purge_batch_size.
• Commandline: --innodb_purge_threads=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 0
• Range: 0 to 1
• Introduced: MariaDB/MySQL 5.5.4

---

innodb_random_read_ahead

• Description: Originally, random read-ahead was always set as an optimization technique, but was removed in MariaDB/MySQL 5.5. innodb_random_read_ahead permits it to be re-instated if set to 1 (0) is default.
• Commandline: --innodb_random_read_ahead=#
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_read_ahead

• Description: If set to linear, the default, XtraDB/InnoDB will automatically fetch remaining pages if there are enough within the same extent that can be accessed sequentially. If set to none, read-ahead is disabled. random has been removed and is now ignored, while both sets to both linear and random. Also see innodb_read_ahead_threshold for more control on read-aheads. Removed in MariaDB 10.0/XtraDB 5.6 and replaced by MySQL 5.6's innodb_random_read_ahead.
• Commandline: innodb-read-ahead=value
• Scope: Global
• Dynamic: Yes
• Data Type: enumeration
• Default Value: linear
• Valid Values: none, random, linear, both
• Removed: MariaDB 10.0/XtraDB 5.6 - replaced by MySQL 5.6's innodb_random_read_ahead

---

innodb_read_ahead_threshold

• Description: Minimum number of pages XtraDB/InnoDB must read from an extent of 64 before initiating an asynchronous read for the following extent.
• Commandline: --innodb_read_ahead_threshold=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 56
• Range: 0 to 64

---

innodb_read_io_threads

• Description: Number of I/O threads for XtraDB/InnoDB reads. You may on rare occasions need to reduce this default on Linux systems running multiple MariaDB servers to avoid exceeding system limits.
• Commandline: --innodb_read_io_threads=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 4
• Range: 1 to 64

---

innodb_read_only

• Description: If set to 1,(0 is default), the server will be read-only. For use in distributed applications, data warehouses or read-only media.
• Commandline: --innodb_read_only=#
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_recovery_stats

• Description: If set to 1 (0 is default) and recovery is necessary on startup, the server will write detailed recovery statistics to the error log at the end of the recovery process. This Percona XtraDB variable has not been ported to XtraDB 5.6.
• Commandline: No
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Removed: MariaDB 10.0/XtraDB 5.6

---

innodb_recovery_update_relay_log

• Description: If set to 1 (0 is default), the relay log info file will be overwritten on crash recovery if the information differs from the InnoDB record. Should not be used if multiple storage engine types are being replicated. Previously named innodb_overwrite_relay_log_info. Removed in MariaDB 10.0/XtraDB 5.6 and replaced by MySQL 5.6's relay-log-recovery
• Commandline: innodb-recovery-update-relay-log={0|1}
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Introduced: XtraDB 5.5.10-20.1
• Removed: MariaDB 10.0/XtraDB 5.6 - replaced by MySQL 5.6's relay-log-recovery

---

innodb_replication_delay

• Description: Time in milliseconds for the slave server to delay the replication thread if innodb_thread_concurrency is reached.
• Commandline: --innodb_replication_delay=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 0
• Range: 0 to 4294967295

---

innodb_rollback_on_timeout

• Description: InnoDB usually rolls back the last statement of a transaction that's been timed out (see innodb_lock_wait_timeout). If innodb_rollback_on_timeout is set to 1 (0 is default), InnoDB will roll back the entire transaction. Before MariaDB/MySQL 5.5, rolling back the entire transaction was the default behavior.
• Commandline: --innodb_rollback_on_timeout
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: 0

---

innodb_rollback_segments

• Description: Specifies the number of rollback segments that XtraDB/InnoDB will use within a transaction. Replaced by innodb_undo_logs in MariaDB 10.0/MySQL 5.6.
• Commandline: --innodb_rollback_segments=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 128
• Range: 1 to 128
• Introduced: MariaDB/MySQL 5.5.11

---

innodb_show_locks_held

• Description: Specifies the number of locks held for each InnoDB transaction to be displayed in SHOW ENGINE INNODB STATUS output.
• Commandline: innodb-show-locks-held=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 10
• Range: 0 to 1000
• Introduced: XtraDB 5.5.8-20.0

---

innodb_show_verbose_locks

• Description: If set to 1, the traditional InnoDB behavior is followed and locked records will be shown in SHOW INNODB STATUS output. If set to 0, the default, only high-level information about the lock is shown.
• Commandline: innodb-show-verbose-locks=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 0
• Range: 0 to 1
• Introduced: XtraDB 5.5.8-20.0

---

innodb_sort_buffer_size

• Description: Size of the sort buffers used for sorting data when an InnoDB index is created, as well as the amount by which the temporary log file is extended during online DDL operations to record concurrent writes. Before MariaDB 10.0/MySQL 5.6, this was not configurable and the current default setting of 1MB was fixed. The larger the setting, the fewer merge phases are required between buffers while sorting. When a CREATE TABLE or ALTER TABLE creates a new index, three buffers of this size are allocated, as well as pointers for the rows in the buffer.
• Commandline: --innodb_sort_buffer_size=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 1048576 (1M)
• Range: 65536 to 67108864
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_spin_wait_delay

• Description: Maximum delay (not strictly corresponding to a time unit) between spin lock polls.
• Commandline: --innodb_spin_wait_delay=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 6
• Range: 0 to 4294967295

---

innodb_stats_auto_recalc

• Description: If set to 1 (the default), persistent statistics are automatically recalculated when the table changes significantly (more than 10% of the rows). Affects tables created or altered with STATS_PERSISTENT=1 (see CREATE TABLE), or when innodb_stats_persistent is enabled. innodb_stats_persistent_sample_pages determines how much data to sample when recalculating.
• Commandline: --innodb_stats_auto_recalc=#
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: ON
• Introduced: MariaDB 10.0/XtraDB 5.6

---

innodb_stats_auto_update

• Description: If set to 0 (1 is default), index statistics will not be automatically calculated except when an ANALYZE TABLE is run, or the table is first opened. Replaced by innodb_stats_auto_recalc in MariaDB 10.0/XtraDB 5.6.
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: 1
• Introduced: XtraDB 5.5.8-20.0
• Removed: XtraDB 5.6 - replaced by innodb_stats_auto_recalc.

---

innodb_stats_method

• Description: Determines how NULLs are treated for XtraDB/InnoDB index statistics purposes. If set to nulls_equal, the default, all NULL index values are treated as a single group. This is usually fine, but if you have large numbers of NULLs the average group size is slanted higher, and the optimizer may miss using the index for ref accesses when it would be useful. If set to nulls_unequal, the opposite approach is taken, with each NULL forming its own group of one. Conversely, the average group size is slanted lower, and the optimizer may use the index for ref accesses when not suitable. Setting to nulls_ignored ignores NULLs altogether from index group calculations. See also Index Statistics, aria_stats_method and myisam_stats_method.
• Commandline: --innodb_stats_method=name
• Scope: Global
• Dynamic: Yes
• Data Type: enumeration
• Default Value: nulls_equal
• Valid Values: nulls_equal, nulls_unequal, nulls_ignored
• Introduced: MariaDB/MySQL 5.5.10

---

innodb_stats_on_metadata

• Description: If set to 1, the default, XtraDB/InnoDB updates statistics when accessing the INFORMATION_SCHEMA.TABLES or INFORMATION_SCHEMA.STATISTICS tables, and when running metadata statements such as SHOW INDEX or SHOW TABLE STATUS. If set to 0, statistics are not updated at those times, which can reduce the access time for large schemas, as well as make execution plans more stable.
• Commandline: --innodb_stats_on_metadata
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: ON
• Introduced: MariaDB/MySQL 5.5.4

---

innodb_stats_persistent

• Description: ANALYZE TABLE produces index statistics, and this setting determines whether they will be stored on disk, or be required to be recalculated more frequently, such as when the server restarts. This information is stored for each table, and can be set with the STATS_PERSISTENT clause when creating or altering tables (see CREATE TABLE).
• Commandline: --innodb_stats_persistent=setting
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: ON
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_stats_persistent_sample_pages

• Description: Number of index pages sampled when estimating cardinality and statistics for indexed columns. Increasing this value will increases index statistics accuracy, but use more I/O resources when running ANALYZE TABLE.
• Commandline: --innodb_stats_persistent_sample_pages=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 20
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_stats_sample_pages

• Description: Gives control over the index distribution statistics by determining the number of index pages to sample. Higher values produce more disk I/O, but, especially for large tables, produce more accurate statistics and therefore make more effective use of the query optimizer. Lower values than the default are not recommended, as the statistics can be quite inaccurate. Deprecated in MariaDB 10.0 - use innodb_stats_transient_sample_pages instead.
• Commandline: --innodb_stats_sample_pages=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 8
• Range: 1 to 264-1
• Deprecated: MariaDB 10.0

---

innodb_stats_transient_sample_pages

• Description: Gives control over the index distribution statistics by determining the number of index pages to sample. Higher values produce more disk I/O, but, especially for large tables, produce more accurate statistics and therefore make more effective use of the query optimizer. Lower values than the default are not recommended, as the statistics can be quite inaccurate. If persistent statistics are used on a table (see innodb_stats_persistent), the setting from innodb_stats_persistent_sample_pages) applies instead.
• Commandline: --innodb_stats_transient_sample_pages=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 8
• Range: 1 to 264-1
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_stats_update_need_lock

• Description: Setting to 0 (1 is default) may help reduce contention of the &dict_operation_lock, but also disables the Data_free option in SHOW TABLE STATUS. This Percona XtraDB variable has not been ported to XtraDB 5.6.
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: 1
• Introduced: XtraDB 5.5.8-20.0
• Removed: MariaDB 10.0/XtraDB 5.6

---

innodb_strict_mode

• Description: If set to 1 (0 is the default), XtraDB/InnoDB will return errors instead of warnings in certain cases, similar to strict SQL mode.
• Commandline: --innodb_strict_mode=#
• Scope: Global, Session
• Dynamic: Yes
• Data Type: boolean
• Default Value: OFF

---

innodb_support_xa

• Description: If set to 1, the default, XA transactions are supported. XA support ensures data is written to the binary log in the same order to the actual database, which is critical for replication and disaster recovery, but comes at a small performance cost. If your database is set up to only permit one thread to change data (for example, on a replication slave with only the replication thread writing), it is be safe to turn this option off.
• Commandline: --innodb_support_xa
• Scope: Global, Session
• Dynamic: Yes
• Data Type: boolean
• Default Value: ON

---

innodb_sync_array_size

• Description: By default 1, can be increased to split internal thread co-ordinating, giving higher concurrency when there are many waiting threads.
• Commandline: --innodb_sync_array_size=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 1
• Range: 1 to 1024
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_sync_spin_loops

• Description: The number of times a thread waits for an XtraDB/InnoDB mutex to be freed before the thread is suspended.
• Commandline: --innodb_sync_spin_loops=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 30
• Range: 0 to 4294967295

---

innodb_table_locks

• Description: If autocommit is set to to 0 (1 is default), setting innodb_table_locks to 1, the default, will cause XtraDB/InnoDB to lock a table internally upon a LOCK TABLE.
• Commandline: --innodb_table_locks
• Scope: Global, Session
• Dynamic: Yes
• Data Type: boolean
• Default Value: ON

---

innodb_thread_concurrency

• Description: Once this number of threads is reached (excluding threads waiting for locks), XtraDB/InnoDB will place new threads in a wait state in a first-in, first-out queue for execution, in order to limit the number of threads running concurrently. A setting of 0, the default, permits as many threads as necessary. A suggested setting is twice the number of CPU's plus the number of disks.
• Commandline: --innodb_thread_concurrency=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 0
• Range: 0 to 1000

---

innodb_thread_concurrency_timer_based

• Description: If set to 1, thread concurrency will be handled in a lock-free timer-based manner rather than the default mutex-based method. Depends on atomic op builtins being available. This Percona XtraDB variable has not been ported to XtraDB 5.6.
• Commandline: innodb-thread-concurrency-timer-based={0|1}
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Removed: MariaDB 10.0/XtraDB 5.6

---

innodb_thread_sleep_delay

• Description: Time in microseconds that XtraDB/InnoDB threads sleep before joining the queue. Setting to 0 disables sleep.
• Commandline: --innodb_thread_sleep_delay=#
• Scope: Global
• Dynamic: Yes
• Data Type: numeric
• Default Value: 10000

---

innodb_track_changed_pages

• Description: For faster incremental backup with Xtrabackup, XtraDB tracks pages with changes written to them according to the redo log and writes the information to special changed page bitmap files. This read-only variable is used for controlling this feature. See also innodb_max_changed_pages and innodb_max_bitmap_file_size.
• Commandline: innodb-track-changed-pages={0|1}
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Introduced: XtraDB 5.1.65-14.0

---

innodb_undo_directory

• Description: Path to the directory (relative or absolute) that InnoDB uses to create separate tablespaces for the undo logs. The default value leaves the undo logs in the same directory as the other log files. Use together with innodb_undo_logs and innodb_undo_tablespaces. Undo logs are most usefully placed on a separate storage device.
• Commandline: --innodb_undo_directory=name
• Scope: Global
• Dynamic: No
• Data Type: string
• Default Value: .
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_undo_logs

• Description: Specifies the number of rollback segments that XtraDB/InnoDB will use within a transaction. By default set to the maximum, 128, it can be reduced to avoid allocating unneeded rollback segments. See the Innodb_available_undo_logs status variable for the number of undo logs available, and Innodb_undo_logs for active undo logs. See also innodb_undo_directory and innodb_undo_tablespaces. Replaces innodb_rollback_segments in MariaDB 10.0/MySQL 5.6.
• Commandline: --innodb_undo_logs=#
• Scope: Global
• Dynamic: Yes
• Data Type: umeric
• Default Value: 128
• Range: 0 to 128
• Introduced: MariaDB 10.0/MySQL 5.6

---

innodb_use_atomic_writes

• Description: Implement atomic writes on FusionIO devices. See FusionIO DirectFS atomic write support for other variables affected when this is set.
• Commandline: innodb-use-atomic-writes={0|1}
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 5.5.31 / XtraDB 5.5.31

---

innodb_use_fallocate

• Description: Preallocate files fast, using operating system functionality. On POSIX systems, posix_fallocate system call is used. Automatically set to 1 when innodb_use_atomic_writes is set - see FusionIO DirectFS atomic write support.
• Commandline: innodb_use_fallocate={0|1}
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: OFF
• Introduced: MariaDB 5.5.31

---

innodb_use_global_flush_log_at_trx_commit

• Description: Determines whether a user can set the variable innodb_flush_log_at_trx_commit. If set to 1, a user cannot reset the value with a SET command, while if set to 1, a user can reset the value of innodb_flush_log_at_trx_commit.
• Commandline: innodb_use_global_flush_log_at_trx_commit={0|1}
• Scope: Global
• Dynamic: Yes
• Data Type: boolean
• Default Value: ON
• Introduced: XtraDB 5.5.8-20.0

---

innodb_use_native_aio

• Description: For Linux systems only, specified whether to use Linux's asynchronous I/O subsystem. Set to 1 by default, it may be changed to 0 at startup if XtraDB/InnoDB detects a problem
• Commandline: --innodb_use_native_aio=#
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: ON
• Introduced: MariaDB/MySQL 5.5.4

---

innodb_use_purge_thread

• Description: Usually with InnoDB, data changed by a transaction is written to an undo space to permit read consistency, and freed when the transaction is complete. Many, or large, transactions, can cause the main tablespace to grow dramatically, reducing performance. This option, introduced in XtraDB 5.1 and removed for 5.5, allows multiple threads to perform the purging, resulting in slower, but much more stable performance.
• Commandline: --innodb-use-purge-thread=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 1
• Range: 0 to 32
• Introduced: XtraDB 5.1
• Removed: XtraDB 5.5

---

innodb_use_sys_malloc

• Description: If set the 1, the default, XtraDB/InnoDB will use the operating system's memory allocator. If set to 0 it will use its own.
• Commandline: --innodb_use_sys_malloc=#
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: ON

---

innodb_use_sys_stats_table

• Description: If set to 1 (0 is default), XtraDB will use the SYS_STATS system table for extra table index statistics. When a table is opened for the first time, statistics will then be loaded from SYS_STATS instead of sampling the index pages. Statistics are designed to be maintained only by running an ANALYZE TABLE. Replaced by MySQL 5.6's Persistent Optimizer Statistics.
• Commandline: innodb-use-sys-stats-table={0|1}
• Scope: Global
• Dynamic: No
• Data Type: boolean
• Default Value: 0
• Introduced: XtraDB 5.5.8-20.0
• Removed: MariaDB 10.0/XtraDB 5.6

---

innodb_version

• Description: InnoDB version number.
• Scope: Global
• Dynamic: No
• Data Type: string

---

innodb_write_io_threads

• Description: Number of I/O threads for XtraDB/InnoDB writes. You may on rare occasions need to reduce this default on Linux systems running multiple MariaDB servers to avoid exceeding system limits.
• Commandline: --innodb_write_io_threads=#
• Scope: Global
• Dynamic: No
• Data Type: numeric
• Default Value: 4
• Range: 1 to 64

---