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

Chapter 7 351
Logging and Recovery
Roll-Forward Recovery
the recommended procedures have been followed. Recovery can be completed for all of the
other specified databases that have been restored from a backup copy and the recovery flag
is enabled, as long as >CONTROL ERRORS is set appropriately (see "DBRECOV >CONTROL" in
chapter 8). This means that ERRORS must be increased by one for each database disabled
for recovery, because an error message occurs each time a database specified in the
>RECOVER command is not enabled for recovery.
MPE/iX Cleanup Mode and Roll-Forward Recovery
In the event of a system failure and subsequent start recovery operation, MPE/iX attempts
to clean up any user log files that were open at the time of the failure. The cleanup
procedure involves writing any records left in the system log file disk buffer to the user log
file. When using roll-forward recovery without this cleanup, records left in memory will
still be lost. You have the option to cancel (from the console) this cleanup procedure if the
log file is on tape.
The advantage of the cleanup procedure is that fewer user log records written just prior to
the failure are lost. For tape files, the disadvantage is the time it takes for the tape to be
rewound and sequentially scanned until the end-of-file is detected so that the remaining
records can be appended to the end.
The TurboIMAGE/XL recovery program DBRECOV does not require the cleanup to be
performed. If it is not performed, however, DBRECOV most likely will report a sequence or
checksum error when the discrepancy caused by the failure is encountered. This would
cause DBRECOV to assume the end-of-file has been reached.
DBRECOV Abort Message
If DBRECOV aborts before recovery completes, the following information is printed:
Abort occurred on database: dbname dbgroup dbaccount
Total database open count: #open Current open count: #open
Process user is: dbuser dbgroup dbaccount Running program: progname
Log file name: logfilename Logging ID: logid
Log file record number: nnnnnnnn Transaction type: xx
Transaction date/time from log record: day, month, dd, year, time
Last successful transaction #: nn
First log record # of last successful transaction: nn
Record the information, set the log file, locate the database store, and contact your HP
support representative.