Architecture and Administration Q002

Todays DBA Question is on Oracle Architecture and Administration.

Which background process and associated database component guarantees that committed data is saved even when the changes have not been recorded in the database files?

1. DBWn and the database buffer cache
2. LGWR ond online redo log file
3. CKPT and control file
4. DBWn and archived redo log file


The answer - 2 LGWR ond online redo log file. The LGWR process writes the redo log buffer entries when a COMMIT occurs. The redo log buffer holds the information on the changes made to the database.

The DBWn process writes dirty buffers to the datafile but is independant of COMMIT. The dirty buffers can be written to the disk before or after a COMMIT. Writing the commited changes to the online redo log file ensures that the changes are not lost in case of a failure.

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