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Friday, February 10, 2006

Resolving a Database Failure

Resolving a Database Failure

Phase I: Diagnose the problem
Phase II: Restore appropriate files
Phase III: Recover the database
Phase IV: Back up the database

Phase I: Diagnose the problem

The first phase is to research the nature of the failure. Use V$ views, data dictionary views, trace and log files, basic operating system commands and Oracle Enterprise Manager to diagnose the problem.
Determine if the database instance is available and the database is open.
Attempt to start the instance.
Shutdown the instance if a problem occurs while starting it or when opening the database.
Check the trace files and alert log files.
Determine the appropriate recovery method:
- Closed database recovery
- Open database, offline tablespace recovery
- Open database, offline tablespace, individual datafile recovery
- Cancel-based recovery
- Time-based recovery
- Change-based recovery


Phase II: Restore Appropriate Files

Before you perform a recovery scenario, determine what files to restore and what state the instance and database must be in to perform the recovery. Remember that the objective is to minimize down time and loss of data, so do not restore files if it is not necessary.

Phase III: Recover the Database

Once the appropriate files are restored, initiate your recovery operation. After completing the recovery, note any proactive measures that can be taken to prevent that type of failure in the future.

Phase IV: Back up the Database

Not all recovery operations require a database backup when they are complete. However, determine whether your database needs to backed up and, if so, perform another backup.

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