Gather backup and logical-log tapes before restoring

Before you restore an entire database system, you must gather backup and logical log tapes. If you changed the names of backup and logical log files, you must also manually rename the files to their original file names.

Backup tapes
Gather all the tapes from your latest level-0 backup that contain the storage spaces you are restoring and any subsequent level-1 or level-2 backups.

Identify the tape that has the latest level-0 backup of the root dbspace on it; you must use this tape first.

Logical-log tapes
If at the time of the archive checkpoint, an open transaction started, gather all logical-log tapes before you perform the level-0 backup.
Gather all the logical-log tapes from the backup after the latest level-0 backup of the storage spaces you are restoring.

When using ontape to create an archive backup of the system, a snapshot of the logical logs is included with the archive. At the end of the archive, the system displays a message that indicates what logical logs are included in the archive. The snapshot is included in the archive so that if any open transactions exist at the time of the backup, those transactions can be reconciled when the archive is restored. Then:
  • If you decide not to replay any logical logs, the system can be brought to a consistent state.
  • If you decide to replay logical logs, the logs contained within the archive backup are discarded and you must replay transactions from the logical log backups.

    The starting log file is the oldest log file containing an open transaction at the time of the last restored archive. You can identify that log file from the message that was displayed when the last archive was restored.

Example:

  • The ontape -s -L 0 command performs a level-0 backup of the system and displays a message that states that the archive contains logs 2-4.
  • The ontape -s -L 1 command performs a level 1 incremental backup of the system and displays a message that states that the archive contains logs 8-9.
If you restore only the level-0 archive and want to replay logs, you need log backups starting with log 2. If you restore the level-0 and level-1 archives and want to replay logs, you need log backups starting with log 8.

The restore of the logical log files uses an archive format, not a log file format. However, the logs contained within the restored archive are in log file format, not an archive format.

File names when restoring from directory

When restoring from a file system directory, ontape requires that storage-space archive and logical-log backup files be named as specified by the TAPEDEV and LTAPEDEV configuration parameters. If files were renamed, including by ontape because of repeated archives and backups, you must manually rename the files to their original file names. To learn about the naming conventions for storage-space archive files and logical-log backup files, see Back up to a directory for the naming conventions of these files.