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Oracle's LGWR

Flushes redo log buffer from the SGA to the online redo log file.

Conditions that trigger a redo log buffer flush

The following conditions trigger a flush from the redo log buffer to the online redo logs:
  • LGWR wakes up every 3 seconds and flushes available redo log.
  • Whenever the redo log buffer is filled up to _log_io_size (_log_io_size defaults to 1/3 of the log buffer size) AND LGWR is not currently writing
  • A transaction commits (unless _wait_for_sync is set to false).