Sybase 12.4.2 Recovery from errors during backup, Checking for backup space, Recovery attempts

CHAPTER 11 Backup and Data Recovery

Example 2 — Incremental backup

TO ’/dev/rmt/0n’ TO ’/dev/rmt/1n’

WITH COMMENT ’Jan 18 full backup of asiquser’

The Catalog Store is backed up first, to /dev/rmt/0n. The IQ Store is backed up next, to both tapes.

To make an incremental backup of the same database, this time using only one tape device, issue the command as follows:

BACKUP DATABASE INCREMENTAL

TO ’/dev/rmt/0n’ SIZE 150

WITH COMMENT ’Jan 30 incremental backup of asiquser’

An example of how to restore this database from these two backups is provided later in this chapter.

Recovery from errors during backup

There are two likely reasons for a failed backup: insufficient space, or hardware failure. Problems with third party software could also cause a failure.

Checking for backup space

BACKUP uses the STACKER and SIZE parameters to determine whether there is enough space for the backup.

•For disk backups, if it decides that you have not provided enough space, it fails the backup before actually writing any of the data.

•If it decides that there is enough space to start the backup, but then runs out before it finishes (for example, if your estimate is incorrect, or if a user in another application fills up a lot of disk space while your backup is in progress), an attended backup prompts you to load a new tape, or to free up disk space. An unattended backup fails if it runs out of space.

•If neither STACKER nor SIZE is specified, backup proceeds until it completes or until the tape or disk is full. If you run out of space, an attended backup prompts you to load a new tape, or to free up disk space; an unattended backup fails.

Recovery attempts

If a backup fails, the backup program attempts to recover as follows:

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