Automatic Backward Recovery Process

Describes the Automatic Backward Recovery process.

By default, Automatic Backward Recovery is disabled.

Important: The handling of transaction log (TLOG) files for Backward Recovery differs depending on whether Forward Recovery is enabled or disabled. See TLOG Files for details.

Automatic Backward Recovery Disabled

During normal Enterprise Server startup or the restart of IMS Database Control, DBC determines whether or not the last execution of DBC shut down properly. If it did not, then DBC automatically scans the most current TLOG to determine if any databases require recovery. However, it does not initiate a recovery process. The name of each database that is determined to be corrupt is written to the ROLLBACK.LST file located by default in the %USERPROFILE%\Documents\Micro Focus User\Enterprise Developer\WORKAREA\ESName directory, and DBC switches to a "suspend" mode. This means that normal transactional processing is prohibited. In this mode, DBC accepts only commands to recover, START, and STOP databases. In this case, you can manually recover any database from a JCL job or using the mfims imsdbu Rollback function. Once you have determined that all databases are properly recovered, use the /DBC RESUME command to restore DBC to full functionality. See IMS Database Control (DBC) Commands for more information.

Automatic Backward Recovery Enabled

You can enable automatic Backward Recovery by setting the ES_IMS_ROLLBACK environment variable in the configuration information for your enterprise server instance to 1. For example:

[ES-Environment]
ES_IMS_ROLLBACK=1

When started by a normal Enterprise Server startup or when triggered by an emergency, the IMS Database Control (DBC) process determines whether or not the last execution of DBC shut down properly. This is done by reading the DBC status file, IMSDBC.DAT, located by default in the %USERPROFILE%\Documents\Micro Focus User\Enterprise Developer\WORKAREA\ESName directory. This file is updated with the status of each IMS database every time the database is shut down and each time its status changes.

When Enterprise Server starts up, DBC reads the most recent status for each database from the IMSDBC.DAT file and restores the databases that shut down normally to their most recent state.

If the IMSDBC.DAT indicates that one or more databases did not shut down properly, DBC invokes Backward Recovery automatically to restore each of those databases using the most recent transaction log (TLOG) file as input.

When recovery of all databases is complete, a summary of databases that were recovered and any warning or error messages returned during the recovery process are written to a list file, which by default is named ROLLBACK.LST and is located in the %USERPROFILE%\Documents\Micro Focus User\Enterprise Developer\WORKAREA\ESName directory.

Note: If DBC is unable to read the IMSDBC.DAT file for any reason, DBC starts up in a "suspend" mode, meaning that normal transactional processing is prohibited. In this mode, DBC accepts only commands to recover, START, and STOP databases. In this case, you can manually recover any database from a JCL job or using the mfims imsdbu Rollback function. Once you have determined that all databases are properly recovered, use the /DBC RESUME command to restore DBC to full functionality. See IMS Database Control (DBC) Commands for more information.