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Lesson 7Standby databases
ObjectiveDiscuss standby databases

Standby Oracle Databases and Mission Critical Systems

There is a growing need to provide maximum availability of mission critical systems. Oracle provides several alternatives to help maintain high availability. One alternative is the use of standby databases. A standby database is a backup copy of your production database. It is maintained on an identically configured but different machine. The names of the disk drives, directory paths, and files should ideally be the same.
As your production system runs, copies of the archive log files are saved to the secondary system and applied to the standby database at regular intervals. This means that the standby database is always a little behind the primary system because there is redo log information that isn't on the secondary system.
In the event of a failure, the secondary system can be activated and the standby database opened for use by your user community. The secondary system becomes your primary system and the standby database becomes your production database. Once the original primary system has been fixed, it can be used as the new secondary system maintaining your standby database.
While the standby database does not contain the most current data, it does maintain high availability with a minimal lose of data.

Creating and maintaining standby databases

You can create a standby database by following these steps:
  1. Backup the data files
  2. Create the standby control file
  3. Archive the current redo log files
  4. Copy the standby control file, data files, and archived redo logs to the standby system
  5. Bring the standby database up in nomount mode
  6. Mount the database as a standby database
  7. Apply the archived log files
Note: More information on standby databases is contained in the Oracle8 release documentation set.
The next lesson is the module wrap-up.