| 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.