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We are planning to make a small change in the Linux file system. To be on the safe side, I thought I would take a SAN-level snapshot of all the drives beforehand. I was thinking I should put the Oracle database in backup mode:

Alter system archive log current;
Alter database begin backup;
-- after the SAN snapshot finish--
Alter database end backup;
Alter system archive log current;

Someone said this command is deprecated from 9i.

My question is, if I go ahead and use this, will it be ok? Or is there another way to do this?

Note: I don't want to use RMAN's full backup as this will take 6 hours.

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The method you describe is ok. This method was the backup method used before Oracle introduced RMAN and is still valid. It is still used by tools that do snapshot backups (like Netapp's backup tool for Oracle) and I often use this in similar situations. You also should make a controlfile backup if all the controlfiles are on these disks.

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  • Thanks, I will also take the ctrl files backup as you advice.
    – leo77
    Aug 18, 2015 at 7:58
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If you can create a snapshot of everything at the same time, you do not even need backup mode.

Backup mode (User Managed Backup) is not deprecated, but RMAN is the preferred tool for making backups.

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  • are you sure I can do the snapshot? what about the unchanged data in the memory, I thought by doing the alter database begin backup will freeze changes to the data files and flush the data disk
    – leo77
    Aug 17, 2015 at 20:04
  • @leo77 That is a common misconception. begin backup freezes only the checkpoint headers, the database will continue writing to datafiles as it normally would, except that part. I have seen some databases being cloned like this with split-mirror or copy-on-write snapshots. Of course you should not base your fallback strategy on a random forum post, so test it first. Create a snapshot, mount it somewhere, and start the database. The database should start after performing a crash recovery.
    – Balazs Papp
    Aug 17, 2015 at 20:28
  • That is right. begin backup only puts the database in a freezed and consistent mode. When you need to go back to your snapshot you loose all changes made after the snapshot unless you still have the archivelogs.
    – Marco
    Aug 17, 2015 at 20:54
  • Thanks for your advice guys, hope everything will be ok and I will not need the snapshot.
    – leo77
    Aug 18, 2015 at 7:59
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I would do a shutdown of the database to be sure that really nothing is written on the filesystem of the SAN. Do you have your archivelogs on the same filesystem? Restart it after you have made the snapshot.

The alter database begin backup; is in the 11g documentation so it must be still valid (have not checked it for 12c).

Do you make full backups with RMAN? In that case you can also do a backup of only the archivelogs. This will also give you the possibility to restore your database in case of total loss.

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  • because its a small change and this can be done online I don't want to shutdown the Database. yes we have the Arch logs on the same file system, We also take full backup every day with RMAN
    – leo77
    Aug 17, 2015 at 19:50
  • Then go for the alter database begin backup;. It is still in the 11g documentation so I guess it is available. If you have the time then first do an RMAN backup of the archivelog files to be really safe.
    – Marco
    Aug 17, 2015 at 19:56

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