Oracle Data Guard overview

Types of standby databases

1. Physical standby

  • exactly block to block same as production database
  • no queries allowed

2. Logical standby

  • Its logically same as production db
  • logs continue to apply in the background

3. Snapshot standby

  • logs are received from primary but not applied until snapshot is converted back to physical stb

4. Active database guard

  • Standby db will be in open mode
  • normal user transactions can also continue on standby