HP 3000 Manuals HP 3000 Manuals
ALLBASE/SQL Interface to True Online Backup
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ALLBASE/SQL files can also be stored along with other files online
without shutting down the DBEnvironment. This enhancement is done to
help you when you do not want to use STORE/STOREONLINE in SQLUtil. The
normal STORE process in SQLUtil requires the DBEnvironment to be shutdown
while taking the backup, whereas, STOREONLINE calls TurboSTORE internally
and the DBEnvironment being backed up is quiesced during the attach
period. After the attach period, the normal activity is resumed.
With the above technique, ALLBASE/SQL users are expected to close their
applications or files when backup is done in SQLUtil. This mechanism
does not provide a complete backup solution to the MPE users.
This becomes more complicated if the system has more than one
DBEnvironment because additional backups must be scheduled on the system.
Consequently, extra overhead is added in terms of time and number of
tapes.
To provide a complete backup solution, the true online backup enhancement
is supported by ALLBASE/SQL. To store an ALLBASE/SQL DBEnvironment online
with all other files in mygroup and myaccount, execute the following
command in the command mode:
STORE @.mygroup.myaccount;*TAPE;ONLINE=START
The store process will do the following:
1. Call an ALLBASE/SQL routine to get the list of files associated
with the DBEnvironment. If the DBEnvironment is in archive-mode,
the list includes DBECon and DBEFiles. In addition the list
includes the log files.
2. Quiesce each DBEnvironment by calling an ALLBASE/SQL routine.
This routine also writes BEGIN ARCHIVE checkpoints if the
DBEnvironment is in archive mode.
3. Make a snapshot of ALLBASE files taken.
4. Unquiesce the DBEnvironment by calling another ALLBASE/SQL
routine.
5. Call an ALLBASE/SQL routine when the store is finished. This
routine indicates successful completion or failure. If the store
is completed successfully, it writes a COMMIT ARCHIVE checkpoint;
otherwise an ABORT ARCHIVE checkpoint is written.
Now if the restore is done, the files are in a consistent state, because
the database files were quiesced when the snapshot was taken. However,
for the archive-mode DBEnvironment, rollforward recovery must be applied.
The other option associated with the ONLINE keyword is END which takes a
snapshot at the end of the backup.
STORE @.mygroup.myaccount;*TAPE;ONLINE=END
In this case, the sequence of calls to ALLBASE/SQL routines remains the
same except that the snapshot occurs after the backup. However, it is
still guaranteed that when the restore is done, files will be the same as
the time when the snapshot was taken. Files are therefore consistent.
This enhancement acts as an interface to True Online Backup and allows
the DBEnvironment to be synchronized when many users are working.[REV
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