Recovery using Archive redo log files

archiveoracleoracle-11grman

As I'm new in using RMAN and archivelog, I've a few doubts regarding to this. My database is Oracle 11g(windows platform). It was previously in noarchivelog mode and recently I've changed it to archivelog mode to backup my data and it started generating archived redo logs in the ARCHIVELOG directory. Each day almost 7 or 9 GB archived redo logs are generating.

Also, I have set my recovery destination and size as 50G and recovery window parameter as 4 days. I know that archive redo log files help me for the point on recovery.

But I am not getting a clear idea about below.

Do I need to delete archivelog mode or will it automatically get cleared?
If I move these archivelog files to other location or disk as backup, should it help me to recover data till that date?
If I need to restore a test database using the production database, is it possible with these archive files? Does it need any other processing?

Thanks in advance.

Best Answer

Do I need to delete archivelog mode or will it automatically get cleared?

Configure archivelog deletetion policy as-

RMAN> CONFIGURE ARCHIVELOG DELETION POLICY TO BACKED UP 1 TIMES TO DISK;

Then you can-

RMAN> DELETE ARCHIVELOG ALL BACKED UP 1 TIMES TO DISK;

Archived redo logs can be deleted automatically by the database or as a result of user-initiated RMAN commands. Only logs in the flash recovery area can be deleted automatically by the database. For archived redo log files in the flash recovery area, the database retains them as long as possible and automatically deletes eligible logs when additional disk space is required.

Configuring an Archived Redo Log Deletion Policy

If I move these archivelog files to other location or disk as backup, should it help me to recover data till that date?

Yes, As long as RMAN can access these files.

If I need to restore a test database using the production database, is it possible with these archive files? Does it need any other processing?

Archived Redo Logs are not sufficient to restore and recover a test database, you need to have full RMAN backup as well. Howerver, if you have physically identical database like Physical Standby database then these archived logs can be used to refresh such databases.

Related Solutions

Why do we need to backup Oracle archive logs along with datafiles

No, you still need archived redo logs. An RMAN backup is not the same as a cold backup; when you restore it you need to apply all the redo generated from the time you started the backup until the time the backup completed in order to get the SCN consistent across all the datafiles and the controlfile.

Let us consider the old fashioned hot backup. In this mode, entire changed database blocks are written to the redo log stream, and the file is copied in the OS. This causes fractured blocks, i.e. the block has changed during the read by the backup. So to recover the database, we restore the DBFs, then the recovery process overlays the changed blocks from the archived redo logs onto the fractured blocks in the file, and we get back to a consistent database.

In an RMAN backup the problem of fractured blocks is eliminated because the blocks are read by Oracle via the SGA not by a Unix tool like cp. However the DBF changes between the time the first block is read and the last block, so it is the same problem, just at a larger scale. That is to say, the SCN changes between the first and last blocks in a backup. The archived redo logs cover this as well.

RMAN gives you the manageability of the catalog, and a means to do hot backups without needing to generate redo at a much higher rate (which puts its own stress on the disks, the backup system etc). However BACKUP DATABASE will not give you a consistent database in and of itself; the only way to do that in Oracle is the cold backup.

Extract Archived Log Files from RMAN Backupset

You probably need to use catalog, because a long time passed since January.

rman target / catalog rman_catalog_user@rman_catalog_db

RUN
{ 
  SET ARCHIVELOG DESTINATION TO '/oracle/temp_restore';
  RESTORE ARCHIVELOG FROM TIME = "to_date('2014-01-19 19:20:00','YYYY-DD-MM HH24:MI:SS')"  
                    UNTIL TIME = "to_date('2014-01-19 20:00:00','YYYY-DD-MM HH24:MI:SS')";
}

Best Answer

Related Solutions

Why do we need to backup Oracle archive logs along with datafiles

Extract Archived Log Files from RMAN Backupset

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