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:
- Buffer cache ==DBWn==> datafiles
- dirty buffer: When buffer in the buffer cache is modified
- Cold buffer: as per LRU, the buffer that hasn’t been used in some time
- DBWn writes cold,dirty buffers to datafiles
- DB_WRITER_PROCESS: specifies number of DBWn processes
- 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