DBA: Backups
Advanced Databases
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Agenda
• Define backup
• Discuss Backup Terminology
• Explain various backup and restore options in
Oracle
• Demonstrate backups in Oracle
Advanced Databases
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Question: What is a Backup?
Advanced Databases
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Backup
A procedure for making extra copies
of data for the purpose of restoration
in case of loss or damage.
Guide to Oracle 10g
Advanced Databases
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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
Advanced Databases
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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.
Backup
Sun (F)
Mon
Tue
Wed
Thu
Fri
Sat
Full
2TB
2TB
2TB
2TB
2TB
2TB
2TB
Incr.
2TB
1GB
1.9GB
2.3GB
2.8GB
Diff
2TB
1GB
0.3GB
0.4GB
0.5GB
1.2GB
1.6GB10g
Guide
to Oracle
0.2GB
0.4GB
Advanced Databases
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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.
Guide to Oracle 10g
Advanced Databases
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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?
Advanced Databases
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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.
Advanced Databases
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Creating Offline (Cold) Backups
1. Shut down database instance
2. Copy specific database files to alternate disk
location
1.
2.
3.
4.
Parameter file
Control files
Datafiles
Not redo logs
3. Restart database instance
Advanced Databases
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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
Guide to Oracle 10g
Advanced Databases
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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
Advanced Databases
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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
Guide to Oracle 10g
Advanced Databases
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Demo – Start and Stop Oracle
• Let’s use OEM to start and stop your Oracle
instance, then create a cold backup
Guide to Oracle 10g
Advanced Databases
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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.
Advanced Databases
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Questions
Advanced Databases
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