CODEWITHSUNDEEP
oracle-databaseloggingbackuparchiverecovery
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Reputation: 29

why we have to backup archive log after backup full DB

i am learning about backup recovery on oracle. i see the script to backup for both DB and archive log. but i think backup archive log maybe can not use when recovering database. all data change in archive log, which was already backup, it in the backup up DB also. for exmaple: i backup DB at 1h00, finish at 2h00 at 2h00, i backup archive log. finish at 2h10

at 4h,DB corrupted, i have to recover DB from DB backup. i think archive log when i backup at 2h00 is not use in that case.

if i incorrect, please correct me. what perpose when we do backup archive log.

Upvotes: 0

Views: 2026

Answers (1)

Popeye
Popeye

Reputation: 35920

An archived redo log file is a copy of one of the filled members of a redo log group. and it must be emptied to create space for the new changes that are constantly happening in your DB. But, If your database is started with archive log mode than before emptying any redo logs it is moved to one of the offline destination files, which is called the archive log.

Archived redo logs are used in case you lost your data due to any situation: DB crashed, data corruption, or any. In such a situation archive logs (from the last backup taken to a time when DB is corrupted) are used. It is described as following with your own example:

  • DB backup was taken at 2h00
  • DB corrupted at 4h00
  • You can use the Good backup that was taken at 2h00 and then use redo logs from archive logs to make all the changes that were happened during 2h00 to 4h00

Your answer: You should take the backup of the archive logs created after the last good backup. All archive logs backup is not needed. and archive log backups should be taken frequently and store it in other than the DB server machine. All the old Archive log backups will be not needed once you take the full DB backup. (You can delete old archive log backup once full DB backup is taken)

You can find more details about the complete recovery of data where archive redo logs are needed from oracle documentation.

Upvotes: 2

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