Last updated on FEBRUARY 03, 2017
Applies to:MySQL Server - Version 4.1 and later
Information in this document applies to any platform.
To guarantee durability of data InnoDB normally flushes log changes to disk at every transaction commit. This behavior may be changed by modification of parameter innodb_flush_log_at_trx_commit , but any configuration may be dangerous depending on OS and hardware configuration.
Additionally, if binary logging is enabled, MySQL Server may flush binary logs on every transaction commit depending on configuration of sync_binlog option.
Following symptoms may be observed:
- COMMIT query appears in slow log
- PROCESSLIST shows some connections hanging in query_end state for several seconds
- INNODB STATUS shows some transactions are commiting data
- OS monitoring tools show high average time for processing disk request operations for disk partition where InnoDB logs or binary logs are located. (E.g. "await" column in output of `iostat -x` on UNIX-like platforms).
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