TurboIMAGE/XL Database Management System Reference Manual (30391-90012)

334 Chapter7
Logging and Recovery
Logging Preparation
backup, and the ONLINE=END option permits the sync point at the end of a
True-Online backup. The ONLINE=START option has the following advantages over
ONLINE=END:
• Allows the database to be restored on an earlier version of MPE/iX.
• Allows faster partial (selective, not @.@.@) restores, since sync point at end requires
RESTORE to read the log files (used for backup) from the end of the last piece of media.
• Spreads log data throughout the backup media, and hence, is less vulnerable to media
errors.
NOTE All True-Online backups created with the sync point at the beginning
(ONLINE=START) can be restored on any MPE/iX system. However, backups
created with the sync point at the end (ONLINE=END) can only be restored
on MPE/iX Release 5.5 or later. If you know at the time of performing the
backup that the database(s) must be restored onto an earlier system, create
the backup with the sync point at the beginning. This is independent of using
user logging and DBRECOV.
To perform roll-forward recovery of your database stored using True-Online backup, the
following requirements must be adhered to:
• Your system must be on MPE/iX Release 5.5 or later.
• If you used the AUTO option with the GETLOG command, ensure that the log files
following the backup are properly synchronized with the backup, especially in a
situation when the last log file number, 999, switches to 001. It is recommended that
you remove (STORE and PURGE) all log files preceding (but not including) this backup.
The SHOW
database ALL command gives the name of the log file from which the
recovery will begin.
• LOG process must remain active when storing the database even when the database is
not open. That is, LOG
logid ,STOP must not be issued before storing the database.
This is because the logging information which is dynamic in nature, is incorporated in
the root file when the database is stored. This dynamic logging information can only be
obtained when the log process is active. It is used later when performing roll-forward
recovery.
• One of the new options, ONLINE=START or ONLINE=END of TurboSTORE/iX, must
be employed when performing the backup.
:FILE musicbk;dev=tape
:STORE music; musicbk;ONLINE=START
• After the backup is completed, purge all log files preceding the one in use when the
backup was initiated. It is essential that you retain the one used when backup was
initiated and the ones following that. These are the log files that will be needed later to
perform roll-forward recovery.
To find out the log file used by True-Online backup, employ the SHOW
database ALL
command of DBUTIL, which displays the time, date, and the log file name used for the