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Navigating the Oracle Backup Maze. Robert Spurzem Senior Product Marketing Manager [email protected] 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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Navigating the oracle backup maze l.jpg

Navigating the Oracle Backup Maze

Robert Spurzem

Senior Product Marketing Manager

[email protected]


Agenda l.jpg

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


How important is backup speed l.jpg

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


Raw vs cooked l.jpg

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.


Rman vs alter tablespace7 l.jpg

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


Offline vs online backups l.jpg

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


Are you a candidate for snapshots l.jpg

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?


Are you a candidate for backup to disk l.jpg

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


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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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