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

Chapter 7 355
Logging and Recovery
Roll-Back Recovery
automatically locates the first log file in the given logging cycle by checking the
beginning of the root file for the logid.
Note that the system boot-up process writes a crash record to the last volume of the
user log set. If a start recovery operation is not performed, this will not occur, causing
DBRECOV to issue a warning.
2. Make a database backup copy in case a system failure occurs during the roll-back
recovery process.
3. Enter the following MPE/iX command string:
:RUN DBRECOV.PUB.SYS
4. Enter the >CONTROL NOSTORE command of DBRECOV to allow recovery to proceed
whether or not the DBSTORE flag is set.
5. Enter the following DBRECOV command (where database name is the name of individual
databases to be rolled back):
>ROLLBACK database name [ ,database name2 ,...., database nameN]
6. Enter all other desired DBRECOV commands (>FILE, >CONTROL with other options
except NOSTORE shown above, and >PRINT). Note that the >FILE command's optional
parameter rmode is not used with the roll-back feature. Refer to chapter 8 for more
information.
7. If you want to recover the databases, enter the DBRECOV >RUN command. Otherwise,
enter the >EXIT command, and DBRECOV terminates, and no recovery takes place.
>RUN
After the >RUN command is given, DBRECOV asks you to mount the log tape (if the log file
medium is tape). Continue the roll-back process as directed by messages returned to
both the console and the terminal screen.
8. If the CHANGELOG command or GETLOG AUTO option was used during logging and the
logging file medium is tape, the following message appears on the terminal screen and
the console:
Reply CONtinue on console when logfile is ready
When the required log file is available, enter the response CON to the console request
from DBRECOV.
Note that the response is in a form similar to REPLY for a tape mount used when storing
or restoring tapes; that is, you need to enter the Process Identification Number (PIN).
After the >RUN command is given, the DBRECOV program recovers the specified databases,
creates specified user-recovery files, and terminates. The DBRECOV program could be
terminated alternatively without any recovery taking place with an >EXIT command.