TurboIMAGE/XL Database Management System Reference Manual MPE/iX V6.5 (30391-90011)

Chapter 7 345
Logging and Recovery
Roll-Forward Recovery
Enabling the Roll-Forward Feature
To enable the roll-forward feature, complete the following sequence:
1. Set the logid and build a log file (if logging to disk) as shown in steps 2 through 6 of
"Logging Preparation" earlier in this chapter.
2. For each particular database, disable access and enable the logging and roll-forward
features by entering the following DBUTIL commands. You can also enable the
MUSTRECOVER option if you wish to use it.
>>DISABLE database name FOR ACCESS
>>ENABLE database name FOR LOGGING,RECOVERY
>>ENABLE database name FOR MUSTRECOVER
Enable any other appropriate flags as discussed in step 7 under "Logging Preparation."
If you plan on using TurboSTORE/iX 7x24 True-Online Backup, your database must be
closed so that you can set these flags to enable the roll-forward feature. For subsequent
true-online backups, you have an option to set the ACCESS and RECOVERY flags.
Remember that before you start the roll-forward recovery, the RECOVER flag must be
enabled and ACCESS flag be disabled.
3. Make a backup copy of the database as discussed in step 8 under "Logging
Preparation."
4. Start the logging process and enable user access to the appropriate databases as shown
in "Logging Maintenance," earlier in this chapter.
Restoring the Database Backup Copy
After a hard system failure, and before roll-forward recovery can begin, you must restore
the database to the state it was in when backup was done. This is done by running the
DBRESTOR program (if DBSTORE was used for backup, as shown below) or by using the
MPE/iX RESTORE facility after purging the damaged database. All databases and files must
be restored to their original group and account, and you must have privileged mode (PM)
capability. Ensure that recovery is enabled and access disabled to prevent user
modifications before the recovery system executes.
If you restored a database backed up with TurboSTORE/iX 7x24 True-Online Backup
(with ONLINE=START or ONLINE=END option), you may need to enable recovery and
disable access. Refer to the DBUTIL >>SHOW command and the following example. If the
flags were set as recommended prior to making the backup copy, no changes are needed.
:RUN DBUTIL.PUB.SYS
.
.
.
>>PURGE ORDERS Note: this is damaged database.
Database ORDERS has been PURGED
>>EXIT