Preparing for Forward Recovery

Describes procedures, prerequisites, and settings necessary for successful database recovery following a hardware or a system failure.

Back Up All Databases

Before you can recover a database, you must have a copy of it to restore. This requires that you perform database backups of all databases and keep backup copies to use for recovery. When a database has a secondary index, you must also have a backup of every secondary index file. Always back up your databases at predetermined recurring intervals. In the event that your database requires recovery, this can minimize the time required to restore the database and minimizes risk when performing the recovery procedure.

Note: The Recovery utility always uses forward recovery log files to update an existing copy of the database even when, in certain situations, the restored backup copy is an empty, initialized database. Therefore, a backup copy of the database is always required for database recovery.

You can use any backup utility you choose. As an option, Micro Focus provides the Image Copy utility, which is part of our IMS Database Forward Recovery feature.

Important: Do not use any Micro Focus utilities on the backup image of a database before attempting to use the database copy for recovery. If you alter the database image in any way, the recovery fails.

Enable Forward Recovery Logging and Set Logfile Location

To use Forward Recovery, you must have the appropriate forward recovery log files in place. By default, forward recovery logging is turned off in Enterprise Server. Once enabled, Enterprise Server creates logs for all online database updates and for all database updates that occur as a result of executing a BMP transaction. To enable forward recovery logging and specify a location for generated forward recovery log files, include the following environment variables and settings in the [ES-Environment] specification entered into the Configuration Information field of Enterprise Server Administration for each enterprise server that updates an IMS database:

Important: Enterprise Server does not create forward recovery log files when databases are updated offline by batch programs running DLI or DBB mode. In these cases, we recommend that you create a backup of each affected database immediately following the completion of each batch job.

Set Up Log File Backup

Because the forward recovery log files are critical to database recovery, you must put something into place to back them up on a regular basis to preserve them. To successfully recover a database, all log files created by database activity that took place after the most recent database backup must be present for use by the recovery utility. All log files that contain records of database activity of any kind are required for a successful recovery, including log files that record only database query activity rather than database updates.

Never delete any log file until after the database has been backed up and you have verified that the log file is no longer needed.