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Lesson 10 Performing recovery through RESETLOGS
Objective Demonstrate how to recover a database after an incomplete recovery with no backup.

Performing Recovery through RESETLOGS

Imagine you have a large database that is required to operate 24 hours, 7 days a week. If a media failure occurs, your recovery time has to be minimized and you have to perform an open database backup after the recovery. However, another media failure happens before you complete the backup after the incomplete recovery. You must now repeat the recovery you performed initially (which you ended with RESETLOGS), and then you must apply the additional logs that were generated after that time. In this situation, you are performing a "recovery through RESETLOGS."

Requirements

Below is a set of criteria for you to evaluate to determine whether a recovery through RESETLOGS can be performed. All of the criteria in the table must be true.

CATEGORY EXPLANATION
Oracle database Must be 7.3.3 and above
Whole backups after RESETLOGS No open or closed whole backup AFTER the database was opened with the RESETLOGS option
Whole backups before RESETLOGS Have an whole open or closed backup BEFORE the database was opened with the RESETLOGS option
Control files You have the control files BEFORE and AFTER you open the database with the RESETLOGS option
Logs All the archived logs and online redo logs are present
Alert log Contains information from the last incomplete recovery

Performing a recovery through RESETLOGS

Recovery through RESETLOGS is a complex process. You should try it only with an experienced DBA at your side. In a real job situation, if you have any doubts about the recovery process, you should contact Oracle technical support. The consequences of mistakes are too high.
In the SlideShow below, suppose the DBA has just completed an incomplete recovery and opened the database with the RESETLOGS option. The current redo log sequence number is #1. He has not yet backed up the current database. Another media failure occurs, damages one of the datafiles and brings down the database. The following SlideShow shows you the steps of recovery through RESETLOGS.
You may also preview all the steps.



Recover Database via Resetlogs
The next lesson explains the concepts behind point-in-time recovery.