Interstage Shunsaku Data Manager Operator's Guide - Microsoft(R) Windows(R) 2000/ Microsoft(R) Windows Server(TM) 2003 - - UNIX -

5.1.1 Relationship between Operation Log Files and Backup Data

The operation log file accumulates Shunsaku update operations as update log data.

When Shunsaku data is updated, update log data will be written to the operation log file. This makes it possible to restore the system to any point after a backup has been made, and to use the API to perform update processes while a backup process is in progress.

The update log data accumulated in the operation log file is discarded after the backup process for the director data file is complete and a backup end declaration is issued. The operation log file therefore contains the log data that has accumulated between the latest backup and the current time.

In the following example, the director data file is backed up after the day's operations have finished.

[Figure : Example of Backing up Director Data Files]

During recovery, the most recently backed up data together with the update log data in the operation log file is applied. This combination makes it possible to recover to any point between the time of the last backup and a time immediately preceding the malfunction.

It is important to ensure that the data to be recovered (director data) and the data needed at recovery time (backup data and operation log) are saved to different disks to prevent both types of data from being damaged at the same time.

If both the director data file and the operation log file are damaged at the same time, the update log data accumulated since the backup was taken will be lost, and it will only be possible to restore the system to the state that existed when the backup was taken.

Furthermore, if the director data file and the backup data are both lost at the same time, the information needed for recovery will also be lost, and it will not be possible to restore the director data file.