Oracle dataguard Interview Questions - Part 2

 

Dataguard Interview Questions Part1 for Part 1

11. How can you monitor the status of Oracle Data Guard?

• Answer:
  • Using the Data Guard Broker (dgmgrl command-line tool or Enterprise Manager).
  • Checking the alert logs of both the primary and standby databases.
  • Monitoring the log transport and apply processes (e.g., v$archive_dest_status, v$dataguard_status).
  • Running queries like SELECT * FROM v$dataguard_stats; to gather statistics.
  • Ensuring the Data Guard broker is running and using its commands to check status.

12. What are the prerequisites for setting up Oracle Data Guard?

• Answer:
  • A primary Oracle database and one or more standby databases.
  • Same version and patch level for both the primary and standby databases.
  • Proper network configuration between primary and standby.
  • Archive log mode enabled on both primary and standby databases.
  • Flashback technology enabled for fast recovery.
  • A proper backup strategy.

13. How can you convert a physical standby to a logical standby?

• Answer: You can convert a physical standby to a logical standby by:
  • Using the DBMS_LOGSTDBY package to prepare the physical standby for conversion.
  • Ensuring that all redo logs have been applied to the standby.
  • Creating a new logical standby using the ALTER DATABASE CONVERT TO LOGICAL STANDBY command.

14. What is the role of Flashback in Oracle Data Guard?

• Answer: Flashback technology enables you to quickly recover from human errors, allowing you to "flash back" to a previous point in time. In the context of Data Guard, Flashback can be used to recover the standby database to a point before a failure or corruption, providing a fast recovery solution.

15. Can a Data Guard setup work with non-Oracle databases?

• Answer: No, Oracle Data Guard is specifically designed for Oracle databases. It is not compatible with non-Oracle databases. However, Oracle GoldenGate can be used for replication and data integration between Oracle and non-Oracle databases.

16. How do you perform a role transition in Data Guard?

• Answer: You perform role transitions using switchover or failover operations:
  • Switchover: A planned transition between the primary and standby roles, typically done for maintenance.
  • Failover: An unplanned role transition triggered by the failure of the primary database.

17. What is Data Guard’s "Apply Lag" and how do you monitor it?

• Answer: Apply Lag is the delay in applying redo logs on the standby database compared to the primary. You can monitor it using v$dataguard_stats or querying v$archive_dest_status to track the log shipping and applying status.

18. What happens if the Data Guard configuration gets out of sync?

• Answer: When a Data Guard configuration gets out of sync, the standby database may fall behind in applying the redo logs. It is important to monitor the system and resolve this issue by applying missing logs or rebuilding the standby.

19. Can Oracle Data Guard be used with RAC (Real Application Clusters)?

• Answer: Yes, Oracle Data Guard can be configured with Oracle RAC. Each instance of the RAC cluster can be part of the Data Guard configuration, and the redo logs are transported from each RAC node in the primary database to the standby databases.

20. What is Data Guard "Log Shipping" and how is it configured?

• Answer: Log shipping refers to the process of transferring redo logs from the primary database to the standby. It is configured by setting the archive log destinations in the init.ora file and by ensuring proper network connectivity between the primary and standby systems.