CHECKPOINT
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Checkpoint is mandatory background process which is requested by DBWR when its being writing data from buffer to data files.
It is used for synchronize the buffer and datafiles
Checkpoint only updates header information to data files whenever DBWR completes writing to datafiles.
Checkpoint update Highest SCN number to all Datafiles from buffer.
Checkpoint occurs from bellow scenario's:
1.DB normal shutdown
2.DBA manual triggered checkpoint.(alter system checkpoint)
3.When its reaches three seconds or PGA_TARGET parameter value.
4.if we defined fast_mttr value then if it reaches fast_mttr.
5.Alter database begin backup mode;
6.when datafile goes offline.
