Database writer process(DBWn)

This is one background process that you can’t ignore for Oracle Certification Exam (1z0 062). Below are important points on DBWn from certification point of view:

  1. Buffer cache  ==DBWn==>  datafiles
  2. dirty buffer: When buffer in the buffer cache is modified
  3. Cold buffer: as per LRU, the buffer that hasn’t been used in some time
  4. DBWn writes cold,dirty buffers to datafiles
  5. DB_WRITER_PROCESS: specifies number of DBWn processes
  6. When DBWn writes automatically?

(a) When server process cannot find a clean reusable buffer after scanning a threshold number of buffers.

(b) DBWn periodically writes buffers to advance the checkpoint

 

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