Oracle Data Guard Interview Question and Answers

9. Explain the architecture of data guard?
  Data guard architecture includes the following components:
  • Primary database – Refers to the production database.
  • Standby database – Refers to a copy of primary or production database. Data guard architecture may have more than one standby database.
  • Log transport service – Manages transfer of achieve log files from primary to standby database.
  • Network configuration – Refers to the network connection between primary and standby database. This connection is based on Oracle Net.
  • Log apply services – Applies archived logs to the standby database.
  • Role management services – manages the role change between primary and standby databases.
  • Data guard broker – Manages data guard creation process and monitors the data guard.
 
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10. What happens when stand by database is not available?
  If standby database is not available and the changes are made in primary database, then there will be a gap in the sequence of archive logs. The information about archive logs in these gaps can be found in the v$archieve_gap view.
 
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11. What is role transition and when does it happen?
  Role transition is the change of role between primary and standby databases. It happen in the following two cases:
  • Switchover, where primary database is switched to standby database and standby database is switched to primary database.
  • Failover, where a standby database can be used as a disaster recovery solution in case of a failure in the primary database.
 
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