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Background processes in an Oracle instance explained
What are the mandatory background processes that play a roll in making an Oracle instance, and what are the functions...
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of those background processes?
The mandatory background processes are: DBWR, LGWR, PMON, SMON and CKPT.
- Database Writer (DBWR): Manages the database buffer cache and writes modified buffers from cache to physical files.
- Log Writer (LGWR): Manages the redo log buffer and writes redo entries from cache to physical files.
- Process Monitor (PMON): Reclaims abnormally terminated user processes, cleans up aborted processes, performs rollback of uncommitted transactions, releases resources held by terminated processes and restarts MTS (multi-threaded server) failed processes.
- System Monitor (SMON): Performs automatic instance recovery at startup, reclaims space used by temporary segments and coalesces contiguous free extents.
- Checkpoint (CKPT): Updates physical files when a checkpoint occurs.
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