Update and Transaction Logging

Transaction logging is a method of continuously backing up the system. Transaction logging records all changes made to files at the moment the changes are made, and writes them to backup medium. Transaction logging allows up-to-the-minute running backup of all file updates, thus providing a measure of system security that goes beyond the backup methods described in other chapters.

Transaction logging has two parts. First, changes made to items and files must be logged; then the logged changes must be processed and written to backup medium. The process of logging item and file updates is called update logging; processing update transactions and writing them to backup medium is the actual transaction logging.

Update logging can run independently of transaction logging, although in most cases the two processes run simultaneously. With update and transaction logging running together, each file update is written almost immediately, thus creating a running backup medium for the database.

This section contains these topics:

Overview to Transaction Logging	Describes update and transaction logging
Update Logging	Describes how to have the update logger log all changes to all files on the database, or to specify which files are to be logged and which are to be excluded.
The Transaction Logger	Describes the transaction logger, which is an independent process, usually a phantom process, that dequeues update transactions and writes them to backup medium.