1. Session - 15 RECOVERY CONTROL - 1 Matakuliah: M0184 / Pengolahan Data Distribusi Tahun: 2005 Versi:

2. OBJECTIVES What is backup and recovery Why we need recovery Recovery manager

3. Backup and Recovery Backup is a copy of data. This copy includes important parts of your database such as the control file and data files. A backup is a safeguard against unexpected data loss and application errors; should you lose your original data, you can use the backup to make it available again.

4. Backup and Recovery Cont’d Recovery in general refers to the various operations involved in restoring, rolling forward, and rolling back a backup.

5. Backup and Recovery Cont’d Backup and recovery in general refers to the various strategies and operations involved in protecting your database against data loss and reconstructing the data should that loss occur.

6. Restoring and Recovering a Database

7. Why we need recovery ? The ability to ensure consistency of the DB in presence of unpredictable failures of both software and hardware components is an essential feature of any DBMS. The role of recovery manager of the DBMS to restore the DB to a consistent state.

8. Recovery Manager Recovery manager has to ensure that, on recovery from failure, either all the effects of a given transaction are permanently recorded in the DB or none of them The principal function of the recovery manager following failure is to identify which transaction have to be undone and which have to be redone, and then perform the necessary undo and redo operations. the

9. Recovery Manager Cont’d The DB Log (also called Journal or Audit trail plays an essential role in this recovery. Audit trail or journal that can be used for anticipating failure are : Log File Checkpoint