Server System Variables

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About Server System Variables

MariaDB has a lot of system variables that can be changed to suit your needs.

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.

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