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Jérôme Dubar

Easily manage dual backup destination with RMAN

Backup on disk with RMAN is great. It’s fast, you can set as many channels as your platform can handle for faster backups. And you can restore as fast as you can read and write files on disk with these multiple channels. As far as you’re using Enterprise Edition because Standard Edition is stuck to a single channel.

Disk space is very often limited and you’ll probably have to find another solution to keep backups longuer if you want to. You can think about tapes or you can connect RMAN to a global backup tool, but it requires additional libraries that are not free, and it definitely adds complexity.

The other solution is to have dual disk destination for the backups. The first one will be the main destination for your daily backups, the other one will be dedicated to long-term backups, maybe on slower disks but with more free space available. This second destination can eventualy be backed up with another tool without using any library.

For the demonstration, assume you have 2 filesystems, /backup is dedicated to latest daily backups and /lt_backup is for long-term backups.

du -hs backup; ls -lrt backup/* | tail -n 8 ; echo ;du -hs lt_backup; ls -lrt lt_backup/* | tail -n 8

4.0K    backup
ls: cannot access backup/*: No such file or directory

4.0K    lt_backup
ls: cannot access lt_backup/*: No such file or directory

 

First of all, take a backup on the first destination:

RMAN> backup as compressed backupset database format '/oracle/backup/%U';

 

This is a small database and backup is done with the default single channel, so there is only two backupsets, one for the datafiles and the other for the controlfile and the spfile:

du -hs backup; ls -lrt backup/* | tail -n 8 ; echo ;du -hs lt_backup; ls -lrt lt_backup/* | tail -n 8

162M    backup
-rw-r-----. 1 oracle oinstall 168067072 Aug 15 01:27 backup/2btaj0mt_1_1
-rw-r-----. 1 oracle oinstall   1130496 Aug 15 01:27 backup/2ctaj0nm_1_1

4.0K    lt_backup
ls: cannot access lt_backup/*: No such file or directory

 

It’s quite easy to move the backup to the long term destination with RMAN:

RMAN> backup backupset all format '/oracle/lt_backup/%U' delete input;

 

BACKUP BACKUPSET with DELETE INPUT is basically the same as a system mv or move. But it does not require to recatalog the backup files as RMAN is doing this automatically.

Now our backup is located in the second destination:

du -hs backup; ls -lrt backup/* | tail -n 8 ; echo ;du -hs lt_backup; ls -lrt lt_backup/* | tail -n 8

4.0K    backup
ls: cannot access backup/*: No such file or directory

162M    lt_backup
-rw-r-----. 1 oracle oinstall 168067072 Aug 15 01:28 lt_backup/2btaj0mt_1_2
-rw-r-----. 1 oracle oinstall   1130496 Aug 15 01:28 lt_backup/2ctaj0nm_1_2

 

You can see here that backup filename has changed: last number increased. Oracle knows that this is the second copy of these backupsets (even the first ones don’t exist anymore).

Like a mv command you can put again your backup in previous destination:

RMAN> backup backupset all format '/oracle/backup/%U' delete input;

162M    backup
-rw-r-----. 1 oracle oinstall 168067072 Aug 15 01:29 backup/2btaj0mt_1_3
-rw-r-----. 1 oracle oinstall   1130496 Aug 15 01:29 backup/2ctaj0nm_1_3

4.0K    lt_backup
ls: cannot access lt_backup/*: No such file or directory

 

All the backupsets are now back to the first destination only, and you can see another increase on the filename. And RMAN catalog is up-to-date.

Now let’s make the first folder the default destination for the backups, and go for compressed backupset as a default behavior:

RMAN> CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO COMPRESSED BACKUPSET ;
RMAN> CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT '/oracle/backup/%U';

 

Now you only need a 2-word command to backup the database:

RMAN> backup database;

 

New backup is in first destination as expected:

du -hs backup; ls -lrt backup/* | tail -n 8 ; echo ;du -hs lt_backup; ls -lrt lt_backup/* | tail -n 8

323M    backup
-rw-r-----. 1 oracle oinstall 168067072 Aug 15 01:29 backup/2btaj0mt_1_3
-rw-r-----. 1 oracle oinstall   1130496 Aug 15 01:29 backup/2ctaj0nm_1_3
-rw-r-----. 1 oracle oinstall 168050688 Aug 15 01:35 backup/2dtaj15o_1_1
-rw-r-----. 1 oracle oinstall   1130496 Aug 15 01:35 backup/2etaj16h_1_1

4.0K    lt_backup
ls: cannot access lt_backup/*: No such file or directory

 

Suppose you want to move the oldest backups, those done before 1.30AM:

RMAN> backup backupset completed before 'TRUNC(SYSDATE)+1.5/24' format '/oracle/lt_backup/%U' delete input;

 

Everything is working as expected, latest backup is still in the first destination, and the oldest one is in the lt_backup filesystem. With another increase of the number ending the filename:

du -hs backup; ls -lrt backup/* | tail -n 8 ; echo ;du -hs lt_backup; ls -lrt lt_backup/* | tail -n 8

162M    backup
-rw-r-----. 1 oracle oinstall 168050688 Aug 15 01:35 backup/2dtaj15o_1_1
-rw-r-----. 1 oracle oinstall   1130496 Aug 15 01:35 backup/2etaj16h_1_1

162M    lt_backup
-rw-r-----. 1 oracle oinstall 168067072 Aug 15 01:38 lt_backup/2btaj0mt_1_4
-rw-r-----. 1 oracle oinstall   1130496 Aug 15 01:38 lt_backup/2ctaj0nm_1_4

 

Now that the tests are OK, let’s simulate a real world example. First, tidy up all the backups:

RMAN> delete noprompt backupset;

 

Let’s take a new backup.

RMAN> backup database;

 

Backup is in default destination:

du -hs backup; ls -lrt backup/* | tail -n 8 ; echo ;du -hs lt_backup; ls -lrt lt_backup/* | tail -n 8

162M    backup
-rw-r-----. 1 oracle oinstall 168050688 Aug 15 01:43 backup/2ftaj1lv_1_1
-rw-r-----. 1 oracle oinstall   1130496 Aug 15 01:43 backup/2gtaj1mo_1_1

4.0K    lt_backup
ls: cannot access lt_backup/*: No such file or directory

 

Let’s take another backup later:

RMAN> backup database;

du -hs backup; ls -lrt backup/* | tail -n 8 ; echo ;du -hs lt_backup; ls -lrt lt_backup/* | tail -n 8

323M    backup
-rw-r-----. 1 oracle oinstall 168050688 Aug 15 01:43 backup/2ftaj1lv_1_1
-rw-r-----. 1 oracle oinstall   1130496 Aug 15 01:43 backup/2gtaj1mo_1_1
-rw-r-----. 1 oracle oinstall 168181760 Aug 15 02:00 backup/2htaj2m4_1_1
-rw-r-----. 1 oracle oinstall   1130496 Aug 15 02:01 backup/2itaj2mt_1_1

4.0K    lt_backup
ls: cannot access lt_backup/*: No such file or directory

 

Now let’s move the oldest backup to the other folder:

RMAN> backup backupset completed before 'TRUNC(SYSDATE)+2/24' format '/oracle/lt_backup/%U' delete input;

du -hs backup; ls -lrt backup/* | tail -n 8 ; echo ;du -hs lt_backup; ls -lrt lt_backup/* | tail -n 8

162M    backup
-rw-r-----. 1 oracle oinstall 168181760 Aug 15 02:00 backup/2htaj2m4_1_1
-rw-r-----. 1 oracle oinstall   1130496 Aug 15 02:01 backup/2itaj2mt_1_1

162M    lt_backup
-rw-r-----. 1 oracle oinstall 168050688 Aug 15 02:02 lt_backup/2ftaj1lv_1_2
-rw-r-----. 1 oracle oinstall   1130496 Aug 15 02:02 lt_backup/2gtaj1mo_1_2

 

Storing only the oldest backups in the long-term destination is not so clever, imagine you loose your first backup destination? It could be great to have the latest backup in both destinations. You can do that with a BACKUP BACKUPSET COMPLETED AFTER and no DELETE INPUT for basically the same as a cp or copy command:

RMAN> backup backupset completed after 'TRUNC(SYSDATE)+2/24' format '/oracle/lt_backup/%U';

du -hs backup; ls -lrt backup/* | tail -n 8 ; echo ;du -hs lt_backup; ls -lrt lt_backup/* | tail -n 8

162M    backup
-rw-r-----. 1 oracle oinstall 168181760 Aug 15 02:00 backup/2htaj2m4_1_1
-rw-r-----. 1 oracle oinstall   1130496 Aug 15 02:01 backup/2itaj2mt_1_1

323M    lt_backup
-rw-r-----. 1 oracle oinstall 168050688 Aug 15 02:02 lt_backup/2ftaj1lv_1_2
-rw-r-----. 1 oracle oinstall   1130496 Aug 15 02:02 lt_backup/2gtaj1mo_1_2
-rw-r-----. 1 oracle oinstall 168181760 Aug 15 02:03 lt_backup/2htaj2m4_1_2
-rw-r-----. 1 oracle oinstall   1130496 Aug 15 02:03 lt_backup/2itaj2mt_1_2

 

That’s it, you now have a first destination for newest backups, and a second one for all the backups. And you just have to schedule these 2 BACKUP BACKUPSET after your daily backup of your database.

Note that backups will stay in both destinations until they reach the retention limit you defined for your database. The DELETE OBSOLETE will purge the backupsets wherever they are and delete all the known copies.

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Jérôme Dubar
Jérôme Dubar

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