1. Introduction to Oracle Backup and Recovery
Darl Kuhn, Regis University

2. Backup and Recovery Planning
How valuable is your data?
How much data can you lose?
Is the data easily recreated?
Mean time to recovery requirements (MTTR)
Availability requirements
Disaster recovery requirements (DR)
Test Plan
How much money can you spend?

3. Backup and Recovery DBAs must be knowledgeable of backup and recovery
Arguably the most critical skill for a DBA to possess
Must know how to architect backups
Must know how to recover in the event of a failure

4. Oracle Architecture
When dealing with backup and recovery, you must know the differences between an Oracle instance and database. When backing up files in an Oracle database, you will mainly be concerned with: control files, datafiles, and archive redo log files. Other file types to backup might be initialization files and network files. Keep in mind for online backups, you never backup the online redo log files, why?

5. Noarchivelog Mode
Noarchivelog mode databases can only be backed up when the database is shutdown.

6. Archivelog Mode
Archivelog mode is required for Hot Backups and RMAN Online backups. Archivelog mode allows you to take online backups, in other words, the database is up and running while the backup is taking place.

7. Archivelog Mode Continued
Advantages
Enables mechanism for recovery of every committed transaction
Enables online backups (Hot or RMAN)
Disadvantages
Requires additional storage
Additional administrative overhead (you need to backup and periodically remove archive redo log files)
Additional process (ARCn) and I/O

8. Enabling Archivelog Mode
SQL> shutdown immediate;
SQL> startup mount;
SQL> alter database archivelog;
SQL> alter database open;
It’s easy to enable archive log mode. However, now you need to consider where the archive redo logs are being written, and how long to keep them on disk before removing them, and how to remove them from disk (let RMAN do it or manually remove them).

9. Location and Management of Archive Redo Logs
If the location for the archive redo logs becomes full and Oracle cannot write archive redo logs to disk, your database will hang.
In a production environment, you must give some detailed thought to the location of the archive redo log files.
You need to ensure there is enough space and that the archive redo logs are backed up and removed on a regular basis.
Do you want to use the Fast Recovery Area (or not).
How long do you keep archive redo logs on disk?
How do you remove the archive redo logs?

10. Types of Backups User Managed Physical Backups
Cold (offline)
Hot (online)
User Managed Logical Backups
Old Export and Import utilities
Data Pump export and import (10g and higher)
Recovery Manager (RMAN)
Offline physical
Online physical
3rd Party Tools

11. User Managed Cold Backup (offline)
Database shutdown during backup
Uses operating system copy command
Cold Backup Steps:
1. Determine location of datafiles, controlfiles, and online redo logs
2. Shutdown immediate, transactional, or normal
3. Copy files to backup location
4. Startup database

12. User Managed Hot Backup (online)
Database must be in archivelog mode
Tablespaces must be altered in and out of backup mode
Database remains online during backup
While tablespace in backup mode:
When a block first changes
Full block written to redo stream
Not just the atomic change vector
Can be significant performance hit
Very common misperception that DBWn stops writing to datafiles during Hot Backup, not true!

13. User Managed Hot Backup Procedure
Hot Backup has more moving parts than a Cold:
1. Ensure database in archivelog mode
2. Determine which files to backup
3. Switch on-line redo logs
4. Alter tablespaces into backup mode (serial or parallel)
5. Use an OS utility to copy datafiles to backup location
6. Alter tablespaces out of backup mode
7. Switch on-line redo logs
8. Copy any archive redo logs generated during backup
9. Backup the controlfile via "alter database backup controlfile to <location/name>";

14. User Managed Logical Backups
Export utility
Data Pump export:
10g and higher
Greatly enhanced performance
Schedule data pump jobs within the server
Control and monitor data pump jobs from a different session
Enhanced ETL operations
The old export utility and the newer Data Guard export utility are referred to as “logical” because the backup file is not a physical copy of the data blocks, rather it’s a backup of the SQL that is required to recreate the objects and then the data to repopulate those objects.

15. Recovery Manager (RMAN)
RMAN is a tool that can be used for backup, restore, and recovery of Oracle databases
First shipped with Oracle version 8.0
Oracle's recommended tool for B&R
No extra license required
Enterprise Edition contains all RMAN features, other editions contain subset of RMAN features.
First stable release of RMAN was around Many DBAs who tried to use RMAN before that release have bad memories of RMAN. But since 8.1.6, RMAN has been very reliable and stable.
Some features of RMAN are only available in the Enterprise Edition of Oracle. RMAN does ship with other editions, but does not contain the full feature set.

16. RMAN Advantages
Easy to use command line mode to issue backup, restore, and recover commands
Accessible through Enterprise Manager
Tablespaces not put in backup mode (this is a huge advantage over Hot Backups)
Incremental backups
Block corruption detection
Configurable I/O features (parallelism)
Logging of backup operations
Integrates with Media Management Layer (MML) software
Compression and encryption
Cross-platform data conversion
Advanced reporting capabilities
Data Recovery Advisor
Automatic backup of the control file and server parameter file (spfile)
RMAN has many, many advantages over user managed Hot/Cold backups. You really should be using RMAN (and not user managed Hot/Cold) backups for backing up your Oracle databases.

17. RMAN 9i New Features Backup optimization Restore optimization
Block level recovery
New features for archive redo log backups
Configurable persistent settings, automatic backup of controlfile, spfile
Simplified syntax
Retention policy
RMAN was greatly enhanced in Oracle Database 9i. Many DBAs began to use RMAN with the release of 9i.

18. RMAN 10g New Features
Make use of Flash Recovery Area (renamed to Fast Recovery Area in 11g)
Change tracking
Incremental merge
Backup duration
Compressed backups
Automatic channel failover
Restore failover
Restore preview
Automatic creation of missing datafiles
Recovery through resetlogs
With each release of Oracle, there are many significant improvements to RMAN functionality.

19. RMAN 11g New Features Data Recovery Advisor.
Enhancements to compression.
Ability to backup large datafiles in parallel.
Enhancements to cloning/duplicating.
Oracle Secure Backup enhancements.
More integration with Data Guard.

20. RMAN 12c New Features Not yet released, Oracle Database 12c.
Currently in Beta.
Should be available ???

21. RMAN Backups Should you use a recovery catalog? Should you use a MML?
What should be the retention policy?
Online or Offline
Database must be in archivelog mode for online RMAN backups
Can be as simple as:
RMAN> backup database;

22. Failures Happen Non-Media Failure Media Failure Process failure
Statement failure
User error
Instance failure
Media Failure
Oracle unable to perform I/O on database file
Requires DBA intervention

23. Crash vs. Media Recovery
On startup, Oracle determines whether crash or media failure situation exists:
IF (cf SCN = df SCN) THEN
Startup normally;
ELSE IF (cf stop SCN = infinity) THEN
SMON performs crash recovery;
ELSE IF (cf SCN > df SCN) THEN
Throw media failure error;
ELSE IF (cf SCN < df SCN) THEN
Throw controlfile too old error;
END IF;
Media failure means there is a critical file that Oracle needs that it cannot read when trying to open the database. This could be a control file, an online redo log file, or a datafile.

24. Restore and Recovery
Restore is copying datafiles back from the backup set
Recovery is apply redo to the datafiles via a “recover” command
Many, many different B&R scenarios
Restore and recovery procedure varies widely depending on:
Type of backup
Type of failure (datafile, controlfile, redo)
Archivelog or noarchivelog mode

25. Noarchivelog Mode Restore
Restore from Cold Backup or an RMAN offline backup
Restores to the point in time the backup was taken
No redo available to restore transactions
Most likely will result in loss of data

26. Archivelog Mode Restore and Recovery
Restore datafiles from:
Cold backup
Hot backup
RMAN online or offline backup
Issue “recover” command to apply redo
SQL> recover database ....
Recovery can be either complete or incomplete

27. Complete Recovery
Complete recovery means that you can recover all transactions ever committed in the database
You're restoring the database to the point in time right before the failure occurred
Complete recovery only available for archivelog mode databases
Complete does not mean that you have to restore and recover all datafiles
Only have to restore and recover datafiles that have experienced media failure

28. Incomplete Recovery All transactions are not restored
Types of incomplete recovery:
Change (SCN)
Time
Log
Basic procedure:
Copy all datafiles back from the backup set
Rollforward to desired point
SQL> alter database open resetlogs;

29. Summary Develop B&R plan that meets business requirements
Wide variety of methods to backup and recover your database
Use RMAN
“Your backup is only as good as the last time you tested it...”