Guidelines for Logical-Log Backup 

The following guidelines apply to logical-log backups on your Informix database with ON-Bar , ON-Archive or ontape .

It is very important to back up the logical log on time. Otherwise, if it completely fills, the database stops processing. You then have to perform Emergency Logical-Log Backup.

Different backup approaches offer differing levels of protection against a full logical log. For a summary of measures you can take to avoid this problem, see Preventing Emergency Logical-Log Backup.

Note the following when you plan your logical-log backups:

SAP strongly recommends you to run your production database with logical-log backup enabled. Make sure that the LTAPEDEV parameter is not set to /dev/null on UNIX or nul on Windows NT. Refer to Editing the ONCONFIG File for ON-Archive (the information on LTAPEDEV applies to ON-Bar, ON-Archive , and ontape ).

In general, continuous is the best kind of logical-log backup, because:

The choice of backup mode depends on the data recovery tool you use:

Refer to Continuous or Manual Logical-Log Backup (ON-Bar).

Refer to Automatic Logical-Log Backup (ON-Archive) and Continuous Logical-Log Backup (ON-Archive).

Refer to Automatic or Continuous Logical-Log Backup (ontape).

To avoid competition with archives ( ON-Archive or ontape ) or database backups ( ON-Bar ) you should assign a dedicated tape device for logical-log backup. You must do this if you are using continuous logical-log backup. If you use the same device, there is a chance that the logical-log backup will be held up due to contention with the archive or database backup. This might lead to a full logical log, and the database then stops processing.

For more information on tape devices, see:

With a slow storage device, the logical-log files might fill up more quickly than they can be backed up. This is more likely to happen with a remote device. The best solution is to use a fast local device (for example, a fast local tape drive).

Certain activities cause the logical log to fill up rapidly, for example, data conversion. Monitor the logical log closely at such times and do the following:

 

See also:

Informix documentation