Choosing an Approach to Backup and Recovery [ ALLBASE/SQL Database Administration Guide ] MPE/iX 5.5 Documentation
ALLBASE/SQL Database Administration Guide
Choosing an Approach to Backup and Recovery
When you configure the DBEnvironment, it runs with nonarchive logging by
default. This is appropriate for data definition and table loading,
since nonarchive logging results in more efficient loading, and usually
there is little or no risk of data corruption.
After data definition and before doing the initial backup, you should
decide which kind of backup, recovery, and logging you want to use for
production. If you choose nonarchive logging, you should do a static
backup using the SQLUtil STORE command. For archive logging, you should
choose one of the following:
* If you have TurboSTORE software, do a concurrent backup using the
SQLUtil STOREONLINE command.
* If you do not have TurboSTORE, issue the following SQL statements
in single user mode in ISQL:
isql=> BEGIN ARCHIVE;
isql=> COMMIT ARCHIVE;
Then immediately exit from ISQL and issue the SQLUtil STORE
command.
Choosing Nonarchive Logging
If you choose nonarchive logging, you should back up the entire
DBEnvironment at frequent intervals. Then, in the event of a media
failure, you can restore the DBEnvironment from the most recent backup
and manually enter all transactions that took place from the time of
backup to the time of the failure. This approach makes sense if you use
the DBEnvironment mainly for read operations, or if you process only a
small number of transactions. With nonarchive logging, you do not back
up the log files.
NOTE You cannot use the SQLUtil STOREONLINE command for DBEnvironment
backups if you want to retain nonarchive logging. For backups of
the DBEnvironment in nonarchive logging mode, use only the SQLUtil
STORE command.
Choosing Archive Logging
If you choose archive logging, you create a backup of the entire
DBEnvironment at periodic intervals (say, once a week) and back up the
log files at shorter intervals (say, every day). In the event of a media
failure, you restore the DBEnvironment first, and then you can apply each
of the stored log files in chronological sequence to the restored copy of
the DBEnvironment until you have rolled forward all completed
transactions. If you wish, you can roll forward to a particular time
prior to the crash by supplying a timestamp for recovery.
Archive logging affords the greatest security for the DBEnvironment. If
you choose archive logging, it is best to place the log on a device that
is different from any of the devices that contain other DBEnvironment
files. For the greatest security, use dual logging with the two logs on
different devices.
Since nonarchive logging is the default, you must explicitly turn archive
logging on. If you have TurboSTORE software, the SQLUtil STOREONLINE
command lets you perform the STORE without stopping the DBEnvironment;
and it sets archive logging mode on for all subsequent activity until you
decide to turn it off with a START DBE NEWLOG statement (omitting the
ARCHIVE option).
NOTE Normally, you use the STOREONLINE command for DBEnvironment backups
if you want to use archive logging. If your MPE/iX system does not
have the TurboSTORE enhancements, you must use the SQLUtil STORE
command instead. The complete procedure for this alternate
approach is presented in a later section, "Static Backup Procedures
in Archive Mode."
MPE/iX 5.5 Documentation