Specify separate devices for storage-space and logical-log backups
When backing up to a tape device, specify different devices for the LTAPEDEV and TAPEDEV parameters in the onconfig file. You can schedule these backups independently of each other. You can create a backup on one device at the same time you continuously back up the logical-log files on the other.
If you specify the same
device for the LTAPEDEV and TAPEDEV, the logical log can fill, which
causes the database server to stop processing during a backup. When this
happens, you have two options.
- Stop the backup to free the tape device and back up the logical-log files.
- Leave normal processing suspended until the backup completes.
Precautions to take when you use one tape device
When only one tape device exists and
you want to create backups while the database server is online, take
the following precautions:
- Configure the database server with a large amount of logical-log space through a combination of many or large logical-log files. (See your Informix® Administrator's Guide.)
- Store all explicitly created temporary tables in a dedicated dbspace and then drop the dbspace before backing up.
- Create the backup when low database activity occurs.
- Free as many logical-log files as possible before you begin the backup.
The logical log can fill up before the backup completes. The backup synchronizes with a checkpoint. A backup might wait for a checkpoint to synchronize activity, but the checkpoint cannot occur until all virtual processors exit critical sections. When database server processing suspends because of a full logical-log file, the virtual processors cannot exit their critical sections and a deadlock results.