Oracle Database Administration backup and recovery
- 1. 4 L E C T U R E 4 DBA: BACKUPS & RECOVERY
- 2. AGENDA • Define backup • Discuss Backup Terminology • Explain various backup and restore options in Oracle • Demonstrate backups in Oracle 2
- 3. 3 B A C K U P QUESTION: WHAT IS A BACKUP?
- 4. 4 A P R O C E D U R E F O R M A K I N G E X T R A C O P I E S O F D A T A F O R T H E P U R P O S E O F R E S T O R A T I O N I N C A S E O F L O S S D A M A G E . BACKUP
- 5. BACKUP TERMINOLOGY • Hot Backup • Cold Backup • Full Backup • Incremental Backup • Differential Backup • Backup Window • Backup Job • On-line • Off-line • Off-Site • Data Compression • Data Deduplication • Data Encryption 5
- 6. TYPES OF BACKUP • A full backup (level 0) is a complete copy of a partition. • An incremental backup (level 1) is an archive of only the files that have changed since the last full backup. • A differential backup (level 2, 3, etc) is an archive of only the file that have changed since the last backup (not necessarily full backup. 6 Backup Sun (F) Mon Tue Wed Thu Fri Sat Full 2TB 2TB 2TB 2TB 2TB 2TB 2TB Incr. 2TB 1GB 1.2GB 1.6GB 1.9GB 2.3GB 2.8GB Diff 2TB 1GB 0.2GB 0.4GB 0.3GB 0.4GB 0.5GB
- 7. SHORT-SIGHTED BACKUPS – WHY? • Why are each of these a bad backup strategy? Advantages / Disadvantages? Only taking Cold, Full Backups One Full Offsite backup Just hot backups Full backups monthly, differentials daily. 7
- 8. LET’S TALK STRATEGY • Ideally we’d like to backup everything all the time and keep it around forever. • Realistically, we cannot do that. • You need a combination of short-term and long- term strategies. For example: • At least 3 copies of the data, 1 off site. • Hot backups for convince, cold backups for insurance D/R. • Test your restore process, at multiple levels. • Others? 8
- 9. DATABASE BACKUP AND RECOVERY • Important database administration support tasks include: • Backup • Offline/cold • Online/hot • Recovery • Restore Entire tablespaces • Build test / dev environments from restores • Recover missing / erroneous data in tables. 9
- 10. CREATING OFFLINE (COLD) BACKUPS 1. Shut down database instance 2. Copy specific database files to alternate disk location 1. Parameter file 2. Control files 3. Datafiles 4. Not redo logs 3. Restart database instance 10
- 11. CREATING ONLINE (HOT) BACKUPS 1. Place database instance in ARCHIVELOG mode 2. Back up control file 3. Back up datafiles 4. Instruct database to write current contents of redo log files to archive files - Create backup copies of archive log files 11
- 12. DATABASE RECOVERY • Process of restoring database from either cold or hot backup files • Necessary after database failure • Cold backup recovery: • Shut down database • Restore backed up control file and datafiles to database server • Restart database 12
- 13. DATABASE RECOVERY (CONTINUED) • Hot backup recovery: • Recover database to point at which last hot backup created • Use control trace file to generate new copy of control file • Restore backup copies of datafiles • Perform media recovery 13
- 14. DEMO – START AND STOP ORACLE • Let’s use OEM to start and stop your Oracle instance, then create a cold backup 14
- 15. ORACLE BACKUP STRATEGIES • Cold backups • Simplest to perform • Satisfactory for databases whose: • Contents do not change very much • Users can tolerate downtime while DBA creates cold backup files • Hot backups • Complex to perform • Better suited for dynamic, mission-critical databases • If you setup a clustered environment you can perform cold backups without loss of service. 15
- 16. 16 ? QUESTIONS