The Safe Restore Process (SRP) enables you to delete files from backup media without first having to restore them back to your production environment. The SRP can be used with either tape or disk-based Net Worker storage devices.
Files on the destination (production) site are not modified during file deletion. The SRP deletes files on your production system after they have successfully been restored to the alternate location specified in the recovery window of your policy, but before any new logs for those files are written into the online redo log file directory.
You can then use incremental backups or delta backups of these directories to back up just new changes since the file was last restored.
You can use the SRP to delete files based on different criteria, such as when one or more files are older than a specified time or number of days, or when they have not been accessed in over a specified time period.
How to carry out this process?
The file deletion operation can be made part of an existing backup-archive policy under the recovery window option. When you select the recovery window for your recovery procedure, you will notice that the recovery window is preconfigured with “restore” and “delete” operations.
Delete operation is used for removing old data from tape after a successful restore operation has taken place. This is either done before starting a new backup session (backup) or at end of the backup session (archive).
If you want to delete files from the disk after successful restore in the backup window, select one of the options for “retention” in the “Tape Retention” section of the recovery window. The retention time is either relative or absolute.
Relative means deleting all files that are older than a set number of days or hours, while absolute means that all deleted files must be at least X days old. Delete operation will only happen when the backup-archive policy has been completed successfully.
You can also use both sets of criteria by entering two different policies with different retention times. This allows you to have different file age limits for disaster recovery and normal backups. You can then restore individual files by using the RBA value so you do not have to restore the entire set of data.
You can use retention with deletion to avoid doing a complete file restoration for files that are older than your retention criteria, but still available on disk. You can also delete all files if they are older than your maximum age or number of days by selecting the appropriate option under “Tape Retention” in the recovery window.
When you select this option it deletes all archived data that is older than the specified time period or number of days without having to do any restores at all.
As the archive logs are deleted after their backup, this will impact performance as new archive logs cannot be written until old ones are removed. This is because Networker expects exact same media to be used during backup and restore operations. You can avoid this by using rotating media pools or rotating virtual tapes.
The safe restore process is designed for tape deletion, but you can use it with disk-based storage devices if you configure a backup device that uses the same naming convention as your disk-based storage devices. The Net Worker Server will then be restored to exactly where it was when the SRP was run.
With disk-based storage devices, you do not need to remove old archived files from the disk before running an SRP session. You can simply remove all archived files by selecting one of the options in the “Tape Retention” section in the recovery window after completing your SRP session (after deleting the required data).
DELETING FILES USING THE SRP
If you want to delete data from your disk-based storage devices, you should also make sure that the Net Worker Server has been restored to a clean state after restoring it from an SRP. This ensures the deletion process is carried out on all required files and not just those needed for your restore operation.
The same applies if you are deleting old archived files from a file system or Virtual Tape Library (VTL) that uses incremental backups. You need to ensure that restoration of files into an alternate device has been completed successfully before performing a deletion operation.
There are three different options available in the “Tape Retention” section of the recovery window:
- Delete all aged archives from media without doing any restores
- Delete all aged archives from media or delete them on disk using the safe restore process (SRP)
- Delete all aged archives whether they are on media or not (requires non-rotating disks)
Conclusion:
The safe restore process (SRP) can be used to delete all aged archives in one operation. This is convenient when you only need to remove old archived data in your environment, but does not reduce the amount of disk space required in any way.
If you want to make the best use of your disk space, you should delete old archive logs manually or by using an appropriate retention policy. You could also create a separate backup-archive policy for disaster recovery that deletes all aged archives after restoration has been completed successfully.
