%META:TOPICINFO{author="ChrisBartram" date="1170389014" format="1.1" version="1.2"}%
%META:TOPICPARENT{name="Hp3000DatabaseLogging"}%
---+ Integrating Database Logging with System Backups on the HP3000

At a minimum, for logging processes which log to disc, you'll likely want to do a :CHANGELOG command against each logging process when you start a system backup. This causes the log process to close the current file and open a new file; allowing you to ensure you have the maximum amount of recoverable data (right up to the point of the start of the backup) on your backup media. Without this, the current log file (which may have tens of thousands of transactions) will not get backed up because it is constantly "in use" by the logging process.

For users with "online" backup packages, a :CHANGELOG is probably sufficient (though consult the documentation with your backup product for their recommendations). This way your users can continue to access the database(s) while the backup runs.

For sites without online backups, you may actually want to STOP the various logging processes when you are about to start the backup (**Note that the :LOG xxx,STOP command, though it returns immediately, may take several seconds to complete, so factor that delay into your backup job stream/script). Once your backup completes, you can :LOG xxx,RESTART the log processes. A side effect of this; if the database is enabled for logging but the log process is not running, users/applications will not be able to open the database -- they get an Image error indicating the log process is not running. This can prevent someone from "sneaking in" and opening a database before the backup gets a chance to lock the file -- which causes your database to not get backed up.


-- Main.ChrisBartram - 18 May 2006