Progress/400
Product Guide


Recovery

The same mechanisms that support transaction control assist in recovering a database after a system or medium failure. The Progress database handles crash recovery by using the before-image (BI) file, and additionally, if you specify it, by using the after-image (AI) file.

DB2/400 recovery relies on the journaling mechanism to support commitment control. Journaling is not automatic. You must manually start, maintain, and stop it. When journaling is started, DB2/400 writes database I/O and changes, or journal entries, to a DB2/400 object called a journal receiver (*JRNRCV). Journal entries are records that DB2/400 writes when database access occurs. Journal entries can be before images or after images. When you start journaling, roll-forward recovery (after images) is the OS/400 default. You can provide crash recovery to a database only when each of the database’s physical files is journaled.


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