Background processes in an Oracle instance explained

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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