Navigating the Oracle Backup Maze

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Navigating the Oracle Backup Maze

• Robert Spurzem
• Senior Product Marketing Manager
• Rspurzem_at_legato.com

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Agenda

• How important is backup speed?
• RAW vs. cooked?
• Logical backups using Export utility
• RMAN vs. Alter Tablespace?
• Offline vs. online?
• Full vs. incremental?
• Snapshots?
• Backup to Disk?
• Future Trends

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How important is backup speed?

• Speed is important to meet the backup window
• Speed is dependent on network bandwidth, devices
  and cpu
• Vendor benchmarks arent real world
  configurations
• Oracle RMAN is not the bottleneck
• Databases greater than 200G media servers are
  recommended
• Restore needs to be tested for speed
• 50G can take over 20 hrs if device and
  operational problems occur

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RAW vs. cooked?

• This is an application decision
• RAW is fast but requires more management
• File systems have more overhead but are easier to
  manage and backup
• VxFS Quick I/O product has advantages
• Makes no difference to RMAN
• RMAN backs up from RAW or Cooked
• RMAN restores from RAW or Cooked
• RMAN can restore from RAW to Cooked or from
  Cooked to RAW

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Logical backups using Export utility

• Export utility is provided with Oracle database
  and is easy to use
• Does not require purchase of a module or agent
  product
• Export examines every data block for consistency
• Export backs up to disk so recovery can be fast
• Export can restore by table within a tablespace
• Can only recovery to a single point-in-time
• Export takes longer than a physical backup
• Full Export requires database to be in RESTRICT
  mode for intertable consistency
• No database access during backup

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RMAN vs. Alter Tablespace?

• ALTER TABLESPACE BEGIN online backup
• Custom scripting required
• Issue with fractured blocks
• Freezes the data file header
• Records the end of backup in the SCN header
• Forces redo logs with recovery from the time of
  the backup
• The redo logs fill faster with the full block
  changes, not the vector changes
• Archiving means the online redo logs will
  continue to fill and archive logs will be used
  must manage disk space.

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RMAN vs. Alter Tablespace?

• RMAN online backup
• Introduced with Oracle 8
• Five years of improvements
• 50 use and growing
• No fractured block issue
• Reads the Oracle block size not the file system
  block size
• Normal operation for redo logs
• Reduces complexity
• Efficient backup to tape
• Multiple device streaming
• Improvements with Oracle9i R2
• Persistent Parameter Configuration
• Restartable backup and restore
• Self Describing Backup

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Offline vs. online backups?

• All depends on the db usage and activity
• Can you shut down the db and for how long?
• Can the backup be completed within the backup
  window?
• No database access during offline backup
• Database server is burdened with two processes
  during online backup
• Archive log space management is required during
  online backup if the database is archiving

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Full vs. incremental backups?

• Full Oracle backups are the norm no question
• Perform full backups once a day
• Backup the archive redo log files every 4 hours
• Incremental backups performed by RMAN have well
  known deficiencies
• Incrementals read the entire database to find the
  changed blocks
• Incrementals have a difficult time streaming the
  tape device

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Are you a candidate for snapshots?

• What is a snapshot?
• Frozen image backup from physical mirror or
  logical snapshot
• Do you require fast recovery? (lt2 hours)
• Does your database need to be up 24x7 80
  utilization no backup window
• For very large databases gt500G that are larger
  than backup window
• RMAN Proxy Backup API
• Array based vs. host based snapshots?
• Are snapshots more complex?

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Are you a candidate for backup to disk?

• The cost of disk is dropping
• 1M/TB -gt 100K/TB -gt 10K/TB -gt 1K/TB
• New ATA drives are the driving factor
• What are the advantages of backing up to disk?
• Faster backup and faster recovery
• What are the disadvantages?
• Adds a second backup process
• Tape backup still required for disaster recovery
  and archival
• Adds potential complexity and management overhead
• Potential for longer recovery times from tape
• Single-step vs. Two-step recovery

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Future trends

• Full data life cycle management
• Automation of entire information protection
• Using snapshots disk backup tape archiving
• Snapshot management
• Efficient block level data protection
• Faster backups and restores
• Reduce media costs
• Ease of management
• Wizards to speed configuration and guide recovery
• Automatic performance tuning

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