What are the steps involved in Instance Recovery ?

Rolling forward to recover data that has not been recorded in data files, yet has been recorded in the on-line redo log, including the contents of rollback segments. Rolling back transactions that have been explicitly rolled back or have not been committed as indicated by the rollback segments regenerated in step a. Releasing any resources (locks) held by transactions in process at the time of the failure. Resolving any pending distributed transactions undergoing a two-phase commit at the time of the instance failure.

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Sep 6th, 2004
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Backup and Recovery

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isro_giri
Profile Answers by isro_giri

Mar 21st, 2006

Just startup your database. Oracle will take care remaining process.While Startup of database in Mount stage controlfile information is getting verified and is going to synchronize with Datafile header and online redolog file by CKPT. While SMON will take care of RollBack and releases the lock held by user process.

Mohammed Abdul Afroze

Mar 25th, 2007

Steps for Instance Recovery.

1.While performing Instance recovery the oracle server identifies the last check point.The current redo log file is the only file needed a log switch always initiates check point.

2.From the last check point,using the current the current redo log file all changes made to the database that are not recorded in the datafile are applied.During the roll forward phase the rbs and userdata are updated.

3.Then the db is open and users can connect to the database.However some data may be locked by the transaction that did not commit during the rollforward phase.

4.Then Smon comes into the picture and start doing all uncommited transaction.If Server process initiates recovery,before smon rollback.Then Server process initiates recovery transaction.

5.In the Final stage,the background process SMON initiates recover when needed.

Chiranjeevi Manne

Mar 30th, 2007

1. Restore datafiles.
2. Recover the database using Archived Redologs

krishna

May 23rd, 2007

Steps involve in recovery
1.Restore backup datafiles
2.Recover using Archive log files
3.apply partial backup
4.recover using redo log files

oracleofdelphi
Profile Answers by oracleofdelphi

Sep 9th, 2009

Crash recovery is performed by SMON when database started after an instance crash or after a shutdown abort.
Since during crash current transactions are present in redolog files and not yet been written to corresponding files so the
SCN number of transactions are not synchronized with datafile headers. so while starting up SMON compares SCN in redologs and datafile headers since its not same it writes committed as well as
uncommitted data present in redolog files to datafiles now this step is called rollforward now datafiles contain both committed and
uncommitted data. During rollforward undo is generated in undo files. Now this undo is applied to datafiles and
uncommitted data is rolled back this is called rollback mechanism instance recovery is one where in RAC setup SMON of one instance performs recovery of other failed instances.