Note the functionalities of various background processes: 1: Perform recovery at instance startup. 2: Free the resources used by a user process when it fails. 3: Cleanup the database buffer cache…

CKPT records checkpoint information in the control file and datafile headers (functionality 7); it does not perform instance recovery (1), free user process resources (2), or manage idle session timeouts (5).

SMON (System Monitor) performs automatic instance recovery when the database restarts after a crash by applying redo data to roll forward committed changes (functionality 1). SMON also periodically coalesces free space and cleans up unused temporary segments left by transactions that did not complete normally (functionality 6). Both responsibilities are core and exclusive to the SMON background process.

PMON handles freeing resources of failed user processes (2), dynamically registering database services with listeners (4), and monitoring idle session timeouts (5); temporary segment cleanup (6) belongs to SMON and checkpoint recording (7) belongs to CKPT.

DBWR writes modified (dirty) blocks from the buffer cache to datafiles; it does not perform instance recovery (1), clean up the buffer cache on process failure (3 - that is PMON's role), or register services with listeners (4).