DBWn writes when
1. Checkpoint
2. Dirty buffers threshold reached
3. No free buffers
4. Timeout
5. RAC ping request
6. Tablespace offline
7. Tablespace read only
8. Table DROP or TRUNCATE
9. Tablespace BEGIN BACKUP
GLWR writes when
1. At commit
2. When one-third full
3. When there is 1MB of redo
4. Every 3 seconds
5. Before DBWn writes
SMON Responsibilites
1. instance recovery:A.Rolls forward changes in the redo logs;B.Opens the database or user access;C.Rolls back uncommitted transactions
2. Coalesces free space ever 3 sec
3. Deallocates temporary segments
PMON
Cleans up after failed processes by
A. Rolling back the transaction
B. Releasing locks
C. Releasing other resources
D. Restarts dead dispatchers
CKPT
1. signalling DBWn at checkpoints
2. Updating datafile headers and control files with checkpoint information