InnoDB System Variables Maximum Value 32 The number of background threads devoted to the  InnoDB  purge operation. Increasing the value creates additional purge threads, which can improve efficiency on systems where DML operations are performed on multiple tables. For related information, see Section 15.8.9, “Purge Configuration” . • innodb_purge_rseg_truncate_frequency Command-Line Format --innodb-purge-rseg-truncate- frequency=# System Variable innodb_purge_rseg_truncate_frequency Scope Global Dynamic Yes SET_VAR  Hint Applies No Type Integer Default Value 128 Minimum Value 1 Maximum Value 128 Command-Line Format --innodb-random-read-ahead[={OFF|ON}] System Variable innodb_random_read_ahead Scope Global Dynamic Yes SET_VAR  Hint Applies No Type Boolean Default Value OFF Enables the random read-ahead technique for optimizing  InnoDB  I/O. For details about performance considerations for different types of read-ahead requests, see Section 15.8.3.4, “Configuring InnoDB Buffer Pool Prefetching (Read-Ahead)” . For general I/O tuning advice, see Section 8.5.8, “Optimizing InnoDB Disk I/O” . • innodb_read_ahead_threshold • innodb_random_read_ahead Defines the frequency with which the purge system frees rollback segments in terms of the number of times that purge is invoked. An undo tablespace cannot be truncated until its rollback segments are freed. Normally, the purge system frees rollback segments once every 128 times that purge is invoked. The default value is 128. Reducing this value increases the frequency with which the purge thread frees rollback segments. innodb_purge_rseg_truncate_frequency  is intended for use with innodb_undo_log_truncate . For more information, see Truncating Undo Tablespaces. 3275 Command-Line Format --innodb-read-ahead-threshold=#