Levels and Frequency of Database Backup (ON-Bar)

Levels and Frequency of Database Backup (ON-Bar)

There are the following levels for Informix database backup (that is, whole-system and storage-space backups) for ON-Bar available with the Informix database server:

Level	Description
0 (full)	Backs up used pages. The most secure but biggest and longest database backup.
1	Backs up all changes since the last level-0 database backup
2	Backs up all changes since the last level-1 database backup

Database backups at levels 1 or 2 are known as "incremental."

Be very careful when using level-1 or level-2 database backups because they depend on the previous level-0 database backup. If the last level-0 database backup is lost or unreadable, existing level-1 or level-2 database backups are useless if the database needs to be restored. For more information about how to check that your data is readable for a restore, see Data Consistency with SAPDBA.

The most secure database backup strategy is to perform a level-0 database backup every day. In the event of a system failure, you can restore your last level-0 database backup and then apply the logs backed up during the day of failure.

SAP recommends that you:

Have enough tape drive capacity to perform unattended full database backups. If this is possible, it becomes much easier to perform frequent full (level-0) database backups with large databases, since you do not need to continually mount new tapes.
Only perform full (level-0) database backups unless the database is so large that incremental (level-1 and level-2) database backups are really necessary. Remember that an incremental database backup is no use on its own. It can only be used with an earlier full database backup.

See also:

Informix documentation