> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/server/security/limiting-size-of-created-disk-temporary-files-and-tables/limiting-size-of-created-disk-temporary-files-and-tables-overview.md). # Limiting Size of Created Disk Temporary Files and Tables Overview Overview of the feature introduced in MariaDB 11.5 to limit disk space used by temporary files and internal on-disk temporary tables to prevent disk exhaustion. {% hint style="info" %} This functionality is available from MariaDB 11.5. {% endhint %} You can limit the size of created disk temporary files and tables.\ When the internal in-memory temporary table is oversize and converting to MyISAM/Aria table to store on disk, this option will limit the max space of tmp\_dir. If a new disk temporary table will cause tmp\_dir over the limitation, then this query will return an error. ## Temporary Space The temporary space includes: * All SQL level temporary files. This includes files for filesort, transaction temporary space, analyze, binlog\_stmt\_cache etc. It does not include engine internal temporary files used for repair, alter table, index pre sorting etc. * All internal on disk temporary tables created as part of resolving a SELECT, multi-source update etc. ## Special Cases * When doing a commit, the last flush of the binlog\_stmt\_cache will not cause an error even if the temporary space limit is exceeded. This is to avoid giving errors on commit. This means that a user can temporary go over the limit with up to [binlog\_stmt\_cache\_size](/docs/server/ha-and-performance/standard-replication/replication-and-binary-log-system-variables.md#binlog_stmt_cache_size). ## System Variables There are two system variables used for controlling this feature: * [max\_tmp\_session\_space\_usage](/docs/server/security/limiting-size-of-created-disk-temporary-files-and-tables/max_tmp_session_space_usage-system-variable.md): Limits the temporary space that a single connection can use. * [max\_tmp\_total\_space\_usage](/docs/server/security/limiting-size-of-created-disk-temporary-files-and-tables/max_tmp_total_space_usage-system-variable.md): Limits the temporary space that all connections can use together. {% hint style="info" %} Both limits are checked on every write that grows a temporary file or temporary table. The global limit is checked first: exceeding it fails the statement with `Global temporary space limit reached`, while exceeding the connection's own limit fails it with `Local temporary space limit reached`. Setting either variable to 0 disables that limit only. {% endhint %} ## Status Variables * [tmp\_space\_used](/docs/server/server-management/variables-and-modes/server-status-variables.md#tmp_space_used) * [max\_tmp\_space\_used](/docs/server/server-management/variables-and-modes/server-status-variables.md#max_tmp_space_used) ## Information Schema * New field in [information\_schema.process\_list](/docs/server/reference/system-tables/information-schema/information-schema-tables/information-schema-processlist-table.md): TMP\_SPACE\_USED ## Noteworthy issue * One has to be careful when using small values for either temporary space limit together with [binary logging](/docs/server/server-management/server-monitoring-logs/binary-log.md) and with non transactional tables. * If a binary log entry for the query is larger than [binlog\_stmt\_cache\_size](/docs/server/ha-and-performance/standard-replication/replication-and-binary-log-system-variables.md#binlog_stmt_cache_size) and one hits either temporary space limit when flushing the entry to disk, the query will abort and the binary log will not contain the last changes to the table. This will also stop the replica! * This is also true for all Aria tables as Aria cannot do rollback (except in case of crashes)! * One way to avoid it is to use [@@binlog\_format=statement](/docs/server/ha-and-performance/standard-replication/replication-and-binary-log-system-variables.md#binlog_format) for queries that update many lot of rows. ## Implementation * All writes to temporary files or internal temporary tables, that increase the file size, are routed through temp\_file\_size\_cb\_func() which updates and checks the temp space usage. * Most of the temporary file monitoring is done inside IO\_CACHE. Temporary file monitoring is done inside the Aria engine. * MY\_TRACK and MY\_TRACK\_WITH\_LIMIT are new flags for ini\_io\_cache(). MY\_TRACK means that we track the file usage. TRACK\_WITH\_LIMIT means that we track the file usage and we give an error if the limit is breached. This is used to not give an error on commit when binlog\_stmt\_cache is flushed. * global\_tmp\_space\_used contains the total tmp space used so far. This is needed to quickly check against max\_tmp\_total\_space\_usage. * Temporary space errors are using EE\_LOCAL\_TMP\_SPACE\_FULL and handler errors are using HA\_ERR\_LOCAL\_TMP\_SPACE\_FULL. This is needed until we move general errors to it's own error space so that they cannot conflict with system error numbers. * Return value of my\_chsize() and mysql\_file\_chsize() has changed so that -1 is returned in the case my\_chsize() could not decrease the file size (very unlikely and will not happen on modern systems). All calls to \_chsize() are updated to check for > 0 as the error condition. * At the destruction of THD we check that THD::tmp\_file\_space == 0 * At server end we check that global\_tmp\_space\_used == 0 * As a precaution against errors in the tmp\_space\_used code, one can set max\_tmp\_session\_space\_usage and max\_tmp\_total\_space\_usage to 0 to disable the tmp space quota errors. * truncate\_io\_cache() function added. * Aria tables using static or dynamic row length are registered in 8K increments to avoid some calls to update\_tmp\_file\_size(). ## See Also * [MDEV-9101](https://jira.mariadb.org/browse/MDEV-9101) - Limit size of created disk temporary files and tables *This page is licensed: CC BY-SA / Gnu FDL* {% @marketo/form formId="4316" %}