Interview QA

Interview QA:
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1. How to perform the user managed backup manually?

If we want to take a user managed backups. First we should be put database is in begin backup mode and the cp all the required file to backup location and change the database mode to end backup.

> ALTER DATABASE BEGIN BACKUP;

$CP *dbf /u02/backup/

> ALTER DATABASE END BACKUP;

2. Why more logs are generated after change the database mode to begin backup?

The two things will happen when the tablespace in backup mode

1.) The datafile header associated with the tablespace in the backup up mode will be in frozen state.So it stops updating the datafile header, but it continually writes into the datafile.

2.) More redos are generated.This is because oracle will write all the changed blocks into the redo log.Normally only the changes are logged into the redo logs.

Datafiles are not freezed, only the datafile headers will be freezed !! So simply imagine that when you put the tablespace in backup mode, Oracle will take a checkpoint and update the datafile headers with checkpoint SCN and there after it is freezed until we take tablespace out of backup mode.

3. CACHE FUSION?