Complete - Incomplete Recovery Concept

Contents:- Concepts, Complete Recovery, Incomplete Recovery

Complete Recovery

Complete Recovery brings the database up to the present, including all committed data changes made to the point in time when the recovery was requested.

Steps

1.   Restored Data Files.

2.   Changes applied by online(redo) and offline(archive) redo log file. (the redo log changes are applied to the data files until the current online log is reached and the most recent transactions have been reentered.  Undo blocks are generated during this process. This is called rolling forward or cache recovery.

3.   Data file containing committed and uncommitted transactions.

4.   Undo Applied ( the undo blocks are used to rollback any uncommitted changes is called as transaction recovery.

5.   Recovered Data Files.

In- Complete or Point-in Time Recovery

In Complete or Point-in Time Recovery brings the database up to a specified point in time in past, before the recovery operation was requested.

In Incomplete Recovery There are missing transactions; any data modifications done between the recovery destination time and the present are lost.

Requirements

Because in many cases there have been some changes made to the database that need to be undone. Recovering to a point in the past is a way to remove the unwanted changes.

Need

A Valid offline or online backup of all the data files made before the recovery point.

All Archive logs from the time of backup until the specified time of recovery.

Steps

1.   Restore Data files from as far back as necessary.

2.   Changes applied to point in time by using offline and online redo log file.

3.   Data file containing committed and uncommitted transactions upto PIT.

4.   Database Opened.

5.   Undo Applied.

6.   PIT- Recovered Data files.