Best Practices for Automatic Failover Using Oracle Data Guard 10g Release 2

Agenda

• Fast-Start Failover Overview
• Fast-Start Failover, Details & Best Practices
  • Failover Processing Flow
  • Failover Events and Monitoring
  • Best Practices
  • Test Results
• Automatic Client Failover
• Questions?

Failover Requirements

• Faster is better
  • Downtime is bad
  • If manual intervention is required, the time it takes to notify administrative staff can be lengthy
• Reliability is a must-have
  • Correct procedure for failover must be followed to minimize data loss (recovery point objective)
• Simplicity is preferred
  • Determining if failure condition warrants a failover adds time & complexity to the failover process
  • Manually rebuilding the old primary following failover consumes time and resources and is error prone

Fast-Start Failover Requirements

• Primary and Target Standby are managed by the Data Guard Broker
• Primary database must be in Maximum Availability mode – synchronous redo shipping
• Primary and target standby must have Flashback Database enabled
• Observer host must have DGMGRL utility installed and must have Oracle Net connectivity to both the primary and target standby

When is a Fast-Start Failover Triggered?

• Network Related Conditions:
  • Failover occurs only if links between primary and observer as well as primary and target standby are down
    • Requires a connection between Observer and standby to enable the Observer to confirm that the configuration is in a synchronized state
• By ensuring that at least two fast-start failover partners are present, conditions such as split-brain scenarios are avoided

Reinstatement after a Fast-Start Failover

• Any attempt to start old primary will stop at the mount state thus preventing split brain
• Once Observer sees the old primary is at the mount state, reinstatement is begun
• The old primary is automatically reinstated as the new standby using flashback database
• New standby is automatically resynchronized with new primary by Data Guard
• Once resynchronized, a switchover can occur if desired – returning all systems to their original roles

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