What is Log Writer and when does LGWR writes to log file?

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LGWR is background database process which is responsible for redo log buffer cache to redo log file.

There are five critical situations when LGWR writes to log file:

  • LGWR writes redo or changed information from redo log buffer cache to redo log files in the database.
  • It is responsible for moving redo buffer information to online redo log files when you commit, and a log switch also occurs.
  • LGWR writes to redo files when the redo log buffer is 1/3 rd full.
  • It also writes for every 3 seconds.
  • Before DBWR writes modified blocks to the datafiles, LGWR writes to the log file
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