Server System Variables

About Server System Variables

MariaDB has a lot of system variables that can be changed to suit your needs. Most of these can be set with command line options.

There are a few ways to see the full list of server system variables:

• While in the mysql client, run:

SHOW VARIABLES;

See SHOW VARIABLES for instructions on using this command.

• From your shell, run mysqld like so:

  mysqld --verbose --help

Setting Server System Variables

There are several ways to set server system variables:

• Specify them on the command line:

shell> ./mysqld_safe --aria_group_commit="hard"

• Specify them in your my.cnf file:

aria_group_commit = "hard"

• Set them from the mysql client using the SET command:

SET GLOBAL aria_group_commit="hard";

List of Server System Variables

New variables in MariaDB are:

key_cache_segments

• Description: The number of segments in a key cache.
• Commandline: --key-cache-segments=#
• Scope: Global
• Dynamic: Yes
• Type: number
• Valid values: 0-64
• Default value: 0 (non-segmented)
• Introduced: MariaDB 5.2.0

aria_group_commit

• Description: Specifies aria group commit mode.
• Commandline: --aria_group_commit="value"
• Alias: maria_group_commit
• Scope: Global
• Dynamic: No
• Type: string
• Valid values:
  • none - Group commit is disabled.
  • hard - Wait the number of microseconds specified by aria_group_commit_interval before actually doing the commit. If the interval is 0 then just check if any other threads have requested a commit during the time this commit was preparing (just before sync() file) and send their data to disk also before sync().
  • soft - The service thread will wait the specified time and then sync() to the log. If the interval is 0 then it won't wait for any commits (this is dangerous and should generally not be used in production)
• Default value: none
• Introduced: MariaDB 5.2

aria_group_commit_interval

• Description: Interval between commits in microseconds (1/1000000c) for other threads to come and do a commit in "hard" mode and sync()/commit at all in "soft" mode. Option only has effect if aria_group_commit is used.
• Commandline: --aria_group_commit_interval=#
• Alias: maria_group_commit_interval
• Scope: Global
• Dynamic: No
• Type: number
• Valid values:
  • Default: 0 (no waiting)
  • 32-bit systems: 0-4294967295
  • 64-bit systems: 0-18446744073709547520
• Introduced: MariaDB 5.2

plugin_maturity

• Description: The lowest acceptable plugin maturity. MySQL will not load plugins less mature than that.
• Commandline: --plugin-maturity=level
• Scope: Global
• Dynamic: No
• Type: enum
• Valid levels: unknown, experimental, alpha, beta, gamma, stable
• Default value: unknown
• Introduced: MariaDB 5.2.1

binlog_checksum

• Description: Enable/Disable binlog checksums.
• Commandline: --binlog_checksum=[0|1]
• Scope: Global
• Access Type: Can be changed dynamically
• Data Type: bool
• Default Value: OFF (0)
• Introduced: MariaDB 5.3

master_verify_checksum

• Description: Verify binlog checksums when reading events from the binlog on the master.
• Commandline: --master_verify_checksum=[0|1]
• Scope: Global
• Access Type: Can be changed dynamically
• Data Type: bool
• Default Value: OFF (0)
• Introduced: MariaDB 5.3

slave_sql_verify_checksum

• Description: Verify binlog checksums when the slave SQL thread reads events from the relay log.
• Commandline: --slave_sql_verify_checksum=[0|1]
• Scope: Global
• Access Type: Can be changed dynamically
• Data Type: bool
• Default Value: ON (1)
• Introduced: MariaDB 5.3

Other Variables are the same as in MySQL. See Server System Variables in the MySQL Manual for the full list of MySQL server system variables.