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Navigating the Oracle Backup Maze

Navigating the Oracle Backup Maze. Robert Spurzem Senior Product Marketing Manager Rspurzem@legato.com. 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?

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Navigating the Oracle Backup Maze

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  1. Navigating the Oracle Backup Maze Robert Spurzem Senior Product Marketing Manager Rspurzem@legato.com

  2. 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

  3. How important is backup speed? • Speed is important to meet the backup window • Speed is dependent on network bandwidth, devices and cpu • Vendor benchmarks aren’t 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

  4. 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

  5. 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

  6. 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.

  7. 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

  8. 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

  9. 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

  10. Are you a candidate for snapshots? • What is a snapshot? • Frozen image backup from physical mirror or logical snapshot • Do you require fast recovery? (<2 hours) • Does your database need to be up 24x7; 80% utilization; no backup window • For very large databases >500G that are larger than backup window • RMAN Proxy Backup API • Array based vs. host based snapshots? • Are snapshots more complex?

  11. Are you a candidate for backup to disk? • The cost of disk is dropping • $1M/TB -> $100K/TB -> $10K/TB -> $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

  12. 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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