Backup and restore of migrated files

Some types of backup can back up a stub or a complete migrated file. Six backup-archive client options control the backup and restore of migrated files.

The backup-archive client and the HSM for Windows client work together. The backup-archive client always maintains a copy of the resident file in the backup pool, whether this file is migrated or not. In other words, for migrated files there are two identical versions of the file on the Tivoli® Storage Manager server. One version is in the HSM pool, created by the HSM for Windows client. And one version is the backup copy in the backup pool, created by the backup-archive client. When you restore files, the backup-archive client can always re-create the resident file from the backup copy, even if the copy in the HSM pool was deleted.

The Skip migrated files option and the Check stub file reparse content option regulate the backup of stub files. The two restore options, Restore as migrated file, and Restore resident if not accessible, define how migrated files are restored. The Reset modified last access date option determines whether the access time is changed when a file is backed up. The access time can affect migration. The Staging Directory option controls where copies of migrated files are temporarily stored by the backup-archive client.

There are some limitations for backing up migrated files:

• You must not use adaptive subfile backup and HSM. You must back up only the entire migrated file. If you use adaptive subfile backup on migrated files, you might not be able to restore migrated files correctly. The backup-archive client does not report any errors or warnings when you do a subfile backup of a migrated file.
• If skipmigrated=yes, the backup operation skips the migrated file. The stub is not backed up and the complete file is not backed up.
• If skipmigrated=no (the default), some backup types can back up the stub or the complete file. A backup has the following results:

  Incremental backup or image backup

  Only an incremental backup or image backup can back up a stub. The object that is backed up depends on whether the Tivoli Storage Manager server contains a current backup copy of the complete file.

  If the Tivoli Storage Manager server contains a current backup copy of the complete file:

  An incremental or image backup backs up the stub.

  If the Tivoli Storage Manager server does not contain a current backup copy of the complete file:

  An incremental or image backup backs up the complete file.

  Incremental-by-date backup

  An incremental-by-date backup does not back up the stub or the complete file.

  Selective backup or archive

  Selective backup or archive does not back up a stub. The complete file is backed up regardless of whether a current backup copy exists on the Tivoli Storage Manager server.

Set the backup and restore options for migrated files in the backup-archive client options file dsm.opt. Use the preferences editor or directly edit the backup-archive dsm.opt options file. You can also specify an option when you start a backup-archive client command in a Command Prompt window.