LGWR abbreviation - Oracle Transaction - log writer

Discussion

• Nirja Shah   -Posted on 23 Sep 15
  - The log writer process (LGWR) is responsible for redo log buffer management—writing the redo log buffer to a redo log file on disk.
  
  - LGWR writes all redo entries that have been copied into the buffer since the last time it wrote.
  
  - The redo log buffer is a circular buffer.
  
  - When LGWR writes redo entries from the redo log buffer to a redo log file, server processes can then copy new entries over the entries in the redo log buffer that have been written to disk.
  
  - LGWR normally writes fast enough to ensure that space is always available in the buffer for new entries, even when access to the redo log is heavy.
  
  - LGWR writes one contiguous portion of the buffer to disk. LGWR writes:
  1. A commit record when a user process commits a transaction
  
  2. Redo log buffers
  - Every three seconds
  - When the redo log buffer is one-third full
  - When a DBWn process writes modified buffers to disk, if necessary

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