# System Variable Differences Between MariaDB 5.5 and MySQL 5.5 The following is a comparison of variables that either appear only in [MariaDB 5.5](https://mariadb.com/docs/release-notes/community-server/old-releases/5.5/changes-improvements-in-mariadb-5-5), or have different default settings in [MariaDB 5.5](https://app.gitbook.com/s/aEnK0ZXmUbJzqQrTjFyb/mariadb-community-server-release-notes/old-releases/release-notes-mariadb-5-5-series/changes-improvements-in-mariadb-5-5.md), and MySQL 5.5. MariaDB and MySQL 5.5.38, with only default plugins enabled, were used for the comparison. The most notable differences are that MariaDB includes, by default, the [Aria](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria) storage engine, uses [Percona's XtraDB instead of Oracle's InnoDB](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/innodb), and has a different [thread pool implementation](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb). For this reason, a default implementation of [MariaDB 5.5](https://mariadb.com/docs/release-notes/community-server/old-releases/5.5/changes-improvements-in-mariadb-5-5) will use more memory than MySQL 5.5. This can be handled with the following rules of thumb: * If you are not using [MyISAM](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine) and don't plan to use [Aria](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria): * Set [key\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine/myisam-system-variables#key_buffer_size) to something very low (16K) as it's not used. * Set [aria\_pagecache\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_pagecache_buffer_size) to what you think you need for handling internal tmp tables that didn't fit in memory. * Normally this is what before you had set for [key\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine/myisam-system-variables#key_buffer_size) (at least 1M). * If you are using [MyISAM](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine) and not planning to use [Aria](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria): * Set [aria\_pagecache\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_pagecache_buffer_size) to what you think you need for handling internal tmp tables that didn't fit in memory. * If you are planning to use [Aria](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria), you should set [aria\_pagecache\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_pagecache_buffer_size) to something that fits a big part of your normal data + overflow temporary tables. The large number of differences between MySQL's and MariaDB's default innodb\* variables (based upon InnoDB/XtraDB differences) are not listed here. Details can be found on the [MariaDB versus MySQL - Compatibility](https://github.com/mariadb-corporation/docs-server/blob/test/release-notes/compatibility-and-differences/system-variable-differences-between-mariadb-and-mysql/system-variable-differences-between-mariadb-and-mysql-unmaintained-series/broken-reference/README.md) page. | Variable | [MariaDB 5.5](https://mariadb.com/docs/release-notes/community-server/old-releases/5.5/changes-improvements-in-mariadb-5-5) | MySQL 5.5 | Notes | | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | [aria\_block\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_block_size) | 8192 | - | The Aria storage engine is only available in MariaDB | | [aria\_checkpoint\_interval](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_checkpoint_interval) | 30 | - | The Aria storage engine is only available in MariaDB | | [aria\_checkpoint\_log\_activity](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_checkpoint_log_activity) | 1048576 | - | The Aria storage engine is only available in MariaDB | | [aria\_force\_start\_after\_recovery\_failures](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_force_start_after_recovery_failures) | 0 | - | The Aria storage engine is only available in MariaDB | | [aria\_group\_commit](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_group_commit) | none | - | The Aria storage engine is only available in MariaDB | | [aria\_group\_commit\_interval](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_group_commit_interval) | 0 | - | The Aria storage engine is only available in MariaDB | | [aria\_log\_file\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_log_file_size) | 1073741824 | - | The Aria storage engine is only available in MariaDB | | [aria\_log\_purge\_type](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_log_purge_type) | immediate | - | The Aria storage engine is only available in MariaDB | | [aria\_max\_sort\_file\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_max_sort_file_size) | 9223372036853727232 | - | The Aria storage engine is only available in MariaDB | | [aria\_page\_checksum](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_page_checksum) | ON | - | The Aria storage engine is only available in MariaDB | | [aria\_pagecache\_age\_threshold](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_pagecache_age_threshold) | 300 | - | The Aria storage engine is only available in MariaDB | | [aria\_pagecache\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_pagecache_buffer_size) | 134217720 | - | The Aria storage engine is only available in MariaDB | | [aria\_pagecache\_division\_limit](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_pagecache_division_limit) | 100 | - | The Aria storage engine is only available in MariaDB | | [aria\_recover](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_recover) | NORMAL | - | The Aria storage engine is only available in MariaDB | | [aria\_repair\_threads](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_repair_threads) | 1 | - | The Aria storage engine is only available in MariaDB | | [aria\_sort\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_sort_buffer_size) | 134217728 | - | The Aria storage engine is only available in MariaDB | | [aria\_stats\_method](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_stats_method) | nulls-unequal | - | The Aria storage engine is only available in MariaDB | | [aria\_sync\_log\_dir](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_sync_log_dir) | NEWFILE | - | The Aria storage engine is only available in MariaDB | | [aria\_used\_for\_temp\_tables](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#aria_used_for_temp_tables) | ON | - | The Aria storage engine is only available in MariaDB | | [binlog-annotate-row-events](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/clients-and-utilities/logging-tools/mariadb-binlog/annotate_rows_log_event#master-option-binlog-annotate-row-events) | OFF | - | Introduced in [MariaDB 5.3](https://mariadb.com/docs/release-notes/community-server/old-releases/5.3/changes-improvements-in-mariadb-5-3) for [replicating](https://github.com/mariadb-corporation/docs-server/blob/test/release-notes/compatibility-and-differences/system-variable-differences-between-mariadb-and-mysql/system-variable-differences-between-mariadb-and-mysql-unmaintained-series/broken-reference/README.md) between [MariaDB 5.3](https://mariadb.com/docs/release-notes/community-server/old-releases/5.3/changes-improvements-in-mariadb-5-3) and MySQL/[MariaDB 5.1](https://mariadb.com/docs/release-notes/community-server/old-releases/5.1/changes-improvements-in-mariadb-5-1). | | [binlog\_checksum](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables) | NONE | - | Specifies the type of BINLOG\_CHECKSUM\_ALG for log events in the [binary log](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/server-monitoring-logs/binary-log). | | [binlog\_optimize\_thread\_scheduling](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables) | ON | - | For optimized kernel thread scheduling. | | [deadlock\_search\_depth\_long](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#deadlock_search_depth_long) | 15 | - | The Aria storage engine is only available in MariaDB | | [deadlock\_search\_depth\_short](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#deadlock_search_depth_short) | 4 | - | The Aria storage engine is only available in MariaDB | | [deadlock\_timeout\_long](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#deadlock_timeout_long) | 50000000 | - | The Aria storage engine is only available in MariaDB | | [deadlock\_timeout\_short](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/aria/aria-system-variables#deadlock_timeout_short) | 10000 | - | The Aria storage engine is only available in MariaDB | | [debug\_no\_thread\_alarm](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#debug_no_thread_alarm) | OFF | - | Disable system thread alarm calls, for debugging or testing | | [engine\_condition\_pushdown](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#engine_condition_pushdown) | OFF | ON | Controlled by [optimizer\_switch](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#optimizer_switch) | | [expensive\_subquery\_limit](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#expensive_subquery_limit) | 100 | - | Used for determining expensive queries for optimization. | | [extra\_max\_connections](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables) | 1 | - | Introduced in the [MariaDB 5.1 threadpool](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb-51-53). | | [extra\_port](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables) | 0 | - | Introduced in the [MariaDB 5.1 threadpool](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb-51-53). | | [ignore\_db\_dirs](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#ignore_db_dirs) | | - | Comma-delimited list of directories in the data directory that are not considered as database directories. Only introduced in MySQL 5.6 | | [in\_transaction](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#in_transaction) | 0 | - | Set to 1 if you are in a transaction, and 0 if not. | | [join\_buffer\_space\_limit](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#join_buffer_space_limit) | 2097152 | - | Maximum size in bytes of the query buffer. See [block-based join algorithms](https://mariadb.com/docs/release-notes/community-server/about/compatibility-and-differences/system-variable-differences-between-mariadb-and-mysql/system-variable-differences-between-mariadb-and-mysql-unmaintained-series/broken-reference). | | [join\_cache\_level](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#join_cache_level) | 2 | - | For determining the join algorithms. See [block-based join algorithms](https://mariadb.com/docs/release-notes/community-server/about/compatibility-and-differences/system-variable-differences-between-mariadb-and-mysql/system-variable-differences-between-mariadb-and-mysql-unmaintained-series/broken-reference). | | [key\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine/myisam-system-variables#key_buffer_size) | 134217728 | 8388608 | Size of the buffer for the index blocks used by MyISAM tables and shared for all threads. | | [key\_cache\_segments](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine/myisam-system-variables#key_cache_segments) | 0 | - | The number of segments in a key cache. See [Segmented Key Cache](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/system-variables/segmented-key-cache). | | [log\_slow\_filter](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#log_slow_filter) | admin, filesort, filesort\_on\_disk, full\_join, full\_scan, query\_cache, query\_cache\_miss, tmp\_table, tmp\_table\_on\_disk | - | For slow query log filtering. | | [log\_slow\_rate\_limit](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#log_slow_rate_limit) | 1 | - | Limits the number of queries logged to the [slow query log](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/server-monitoring-logs/slow-query-log). | | [log\_slow\_verbosity](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#log_slow_verbosity) | '' | - | Controls information to be added to the [slow query log](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/server-monitoring-logs/slow-query-log). See also [Slow Query Log Extended Statistics](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/query-optimizations/statistics-for-optimizing-queries/slow-query-log-extended-statistics). | | [master\_verify\_checksum](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables) | OFF | - | Verify binlog checksums when reading events from the binlog on the master. | | [max\_seeks\_for\_key](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#max_seeks_for_key) | 4294967295 | 4294967295 (32-bit) or 18446744073709547520 (64-bit) | The most key seeks required when searching with an index, regardless of the actual index cardinality. If this value is set lower than its default and maximum, indexes will tend to be preferred over table scans. | | [max\_write\_lock\_count](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#max_write_lock_count) | 4294967295 | 4294967295 (32-bit) or 18446744073709547520 (64-bit) | Read lock requests will be permitted for processing after this many write locks. | | [mrr\_buffer\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#mrr_buffer_size) | 262144 | - | Size of buffer to use when using multi-range read with range access. See [Multi Range Read optimization](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/mariadb-internal-optimizations/multi-range-read-optimization#range-access). | | [myisam\_block\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine/myisam-system-variables#myisam_block_size) | 1024 | - | Block size used for [MyISAM](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine) index pages. | | [myisam\_recover\_options](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-usage/storage-engines/myisam-storage-engine/myisam-system-variables#myisam_recover_options) | DEFAULT | OFF | MyISAM recovery mode. | | new | - | OFF | Used for backward-compatibility with MySQL 4.1, not present in MariaDB | | [old\_mode](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#old_mode) | Empty string | - | Used for getting MariaDB to emulate behavior from an old version of MySQL or MariaDB. See [OLD Mode](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/old_mode). | | [optimizer\_switch](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#optimizer_switch) | [See details](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#optimizer_switch) | | A series of flags for controlling the query optimizer. MariaDB has introduced a number of new settings. | | [plugin\_maturity](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#plugin_maturity) | unknown | - | Minimum acceptable plugin maturity. | | [progress\_report\_time](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#progress_report_time) | 5 | - | See [Progress reporting](https://github.com/mariadb-corporation/docs-server/blob/test/release-notes/compatibility-and-differences/system-variable-differences-between-mariadb-and-mysql/system-variable-differences-between-mariadb-and-mysql-unmaintained-series/broken-reference/README.md). | | [query\_cache\_strip\_comments](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#query_cache_strip_comments) | OFF | - | Whether to strip any comments from the query before searching to see if it exists in the [query cache](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/query-cache). | | [replicate\_annotate\_row\_events](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables) | OFF | - | Tells the slave to reproduce annotate\_rows\_events received from the master in its own binary log. | | [replicate\_do\_db](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables) | empty string | - | See [Dynamic Replication Variables](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-filters). | | [replicate\_do\_table](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables) | empty string | - | See [Dynamic Replication Variables](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-filters). | | [replicate\_events\_marked\_for\_skip](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables) | replicate | - | See [Selectively skipping replication of binlog events](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/server-monitoring-logs/binary-log/selectively-skipping-replication-of-binlog-events). | | [replicate\_ignore\_db](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables) | empty string | - | See [Dynamic Replication Variables](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-filters). | | [replicate\_ignore\_table](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables) | empty string | - | See [Dynamic Replication Variables](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-filters). | | [replicate\_wild\_do\_table](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables) | empty string | - | See [Dynamic Replication Variables](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-filters). | | [replicate\_wild\_ignore\_table](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables) | empty string | - | See [Dynamic Replication Variables](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-filters). | | [rowid\_merge\_buff\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#rowid_merge_buff_size) | 8388608 | - | See [Non-semi-join subquery optimizations](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/query-optimizations/subquery-optimizations/non-semi-join-subquery-optimizations). | | [skip\_replication](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables) | OFF | - | See [Selectively skipping replication of binlog events](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/server-monitoring-logs/binary-log/selectively-skipping-replication-of-binlog-events). | | [slave\_sql\_verify\_checksum](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/standard-replication/replication-and-binary-log-system-variables) | ON | - | Verify binlog checksums when the slave SQL thread reads events from the relay log. | | [thread\_pool\_idle\_timeout](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables) | 60 | - | See [Using the Thread Pool in MariaDB 5.5](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb). | | [thread\_pool\_max\_threads](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables) | 60 | - | See [Using the Thread Pool in MariaDB 5.5](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb). | | [thread\_pool\_min\_threads](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables) | 60 | - | Windows-only. See [Using the Thread Pool in MariaDB 5.5](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb). | | [thread\_pool\_oversubscribe](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables) | 3 | - | See [Using the Thread Pool in MariaDB 5.5](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb). | | [thread\_pool\_size](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables) | Number of processors | 16\* | See [Using the Thread Pool in MariaDB 5.5](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb). \*Only available in MySQL with a commercial plugin. | | [thread\_pool\_stall\_limit](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-system-status-variables) | 500 | 6\* | See [Using the Thread Pool in MariaDB 5.5](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb). \*Only available in MySQL with a commercial plugin. | | [thread\_stack](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#thread_stack) | 294912 | 196608 or 262144 | See [Using the Thread Pool in MariaDB 5.5](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-pool/thread-pool-in-mariadb). | | [userstat](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/server-management/variables-and-modes/server-system-variables#userstat) | OFF | - | Whether to activate MariaDB's [User Statistics](https://app.gitbook.com/s/SsmexDFPv2xG2OTyO5yV/ha-and-performance/optimization-and-tuning/query-optimizations/statistics-for-optimizing-queries/user-statistics) implementation, not available in MySQL. | | Variable | [MariaDB 5.5](https://mariadb.com/docs/release-notes/community-server/old-releases/5.5/changes-improvements-in-mariadb-5-5) | MySQL 5.5 | Notes | ## See Also * [System Variable Differences Between MariaDB 10.1 and MySQL 5.7](https://mariadb.com/docs/release-notes/community-server/about/compatibility-and-differences/system-variable-differences-between-mariadb-and-mysql/system-variable-differences-between-mariadb-and-mysql-unmaintained-series/system-variable-differences-between-mariadb-10-1-and-mysql-5-7) * [System Variable Differences Between MariaDB 10.1 and MySQL 5.6](https://mariadb.com/docs/release-notes/community-server/about/compatibility-and-differences/system-variable-differences-between-mariadb-and-mysql/system-variable-differences-between-mariadb-and-mysql-unmaintained-series/system-variable-differences-between-mariadb-10-1-and-mysql-5-6) * [System Variable Differences Between MariaDB 10.0 and MySQL 5.6](https://mariadb.com/docs/release-notes/community-server/about/compatibility-and-differences/system-variable-differences-between-mariadb-and-mysql/system-variable-differences-between-mariadb-and-mysql-unmaintained-series/system-variable-differences-between-mariadb-100-and-mysql-56) {% @marketo/form formid="4316" formId="4316" %}