Oracle RAC Interview Questions

If you're looking for Oracle RAC Interview Questions for Experienced or Freshers, you are at the right place. There are a lot of opportunities from many reputed companies in the world. According to research, Oracle RAC has a market share of about 1.0%. So, You still have the opportunity to move ahead in your career in Oracle RAC Development. Mindmajix offers Advanced Oracle RAC Interview Questions 2024 that help you in cracking your interview & acquire a dream career as an Oracle RAC Developer.

Top 10 Frequently Asked Oracle RAC Interview Questions

1. What is cache fusion?
2. What is a split brain?
3. Explain the use of interconnect.
4. What is a VIP in RAC use?
5. What is the use of OLR?
6. How do you back up ASM Metadata?
7. What is a rolling upgrade?
8. What are some of the RAC-specific parameters?
9. What is the future of the Oracle Grid?
10. What components of the Grid should I back up?

Oracle RAC Interview Questions And Answers

1. What are the differences between Oracle RAC and Oracle Grid?

Ans: 

RAC	GRID
Single system image available	No single system image
Proprietary interoperability with VIA	No standards available
Single ownership	Multiple Ownerships
Discoverable membership services	Central Index  and decentral information to discover
Moderate throughput	Either too high or too low throughput
Guarantees capacity	High capacity, varies sometimes
Most commodity computers	Commodity and High-end computers
Centralized user management	Distributed user management
Centralized resource management	Distributed resource management
Central allocation and scheduling	DecentraliDistributed allocation and scheduling

2. What is cache fusion?

Ans: In a RAC environment, it is the combining of data blocks, which are shipped across the interconnect from remote database caches (SGA) to the local node, in order to fulfill the requirements for a transaction (DML, Query of Data Dictionary).

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3. What is a split brain?

Ans: When database nodes in a cluster are unable to communicate with each other, they may continue to process and modify the data blocks independently. If the same block is modified by more than one instance, synchronization/locking of the data blocks does not take place and blocks may be overwritten by others in the cluster. This state is called split brain.

4. What is the difference between Crash recovery and Instance recovery?

Ans: When an instance crashes in a single node database on startup a crash recovery takes place. In a RAC environment, the same recovery for an instance is performed by the surviving nodes called Instance recovery.

5. Explain the use of interconnect?

Ans: It is a private network that is used to ship data blocks from one instance to another for cache fusion. The physical data blocks, as well as data dictionary blocks, are shared across this interconnect.

6. How do you determine what protocol is being used for Interconnect traffic?

Ans: One of the ways is to look at the database alert log for the time period when the database was started.

Related Article: Oracle RAC Tutorial for Beginners

7. What methods are available to keep the time synchronized on all nodes in the cluster?

Ans: Either the Network Time Protocol(NTP) can be configured or in 11gr2, Cluster Time Synchronization Service (CTSS) can be used.

8. What file components in RAC must reside on shared storage?

Ans: Spfiles, ControlFiles, Datafiles, and Redolog files should be created on shared storage.

9. Where does the Clusterware write when there is a network or Storage missed heartbeat?

Ans: The network ping failure is written in $CRS_HOME/log

10. How do you find out what OCR backups are available?

Ans: The OCR config - shows backup can be run to find out the automatic and manually run backups.

11. If your OCR is corrupted what options do have to resolve this?

Ans: You can use either the logical or the physical OCR backup copy to restore the Repository.

12. How do you find out what object has its blocks being shipped across the instance the most?

Ans: You can use the dba_hist_seg_stats.

13. What is a VIP in RAC use?

Ans: The VIP is an alternate Virtual IP address assigned to each node in a cluster. During a node failure, the VIP of the failed node moves to the surviving node and relays to the application that the node has gone down. Without VIP, the application will wait for TCP timeout and then find out that the session is no longer live due to the failure.

14. How do we know which database instances are part of a RAC cluster?

Ans: You can query the V$ACTIVE_INSTANCES view to determine the member instances of the RAC cluster.

15. What is OCLUMON used for in a cluster environment?

Ans: The Cluster Health Monitor (CHM) stores operating system metrics in the CHM repository for all nodes in a RAC cluster. It stores information on CPU, memory, process, network, and other OS data, This information can later be retrieved and used to troubleshoot and identify any cluster-related issues.

It is a default component of the 11gr2 grid install. The data is stored in the master repository and replicated to a standby repository on a different node.

16. What would be the possible performance impact in a cluster if a less powerful node (e.g. slower CPUs) is added to the cluster?

Ans: All processing will show down to the CPU speed of the slowest server.

17. What is the use of OLR?

Ans: Oracle Local repository contains information that allows the cluster processes to be started up with the OCR being in the ASM storage system. Since the ASM file system is unavailable until the Grid processes are started up a local copy of the contents of the OCR is required which is stored in the OLR.

18. What is the default memory allocation for ASM?

Ans: In 10g the default SGA size is 1G in 11g it is set to 256M and in 12c ASM it is set back to 1G. 

Related Article: Overview of Oracle RAC Resource Mastering

19. How do you back up ASM Metadata?

Ans: You can use md_backup to restore the ASM disk group configuration in case of ASM disk group storage loss.

20. What files can be stored in the ASM disk group?

Ans: In 11g the following files can be stored in ASM disk groups.

• Datafiles
• Redo logfiles
• Spfiles

In 12c the files below can also now be stored in the ASM Diskgroup

• Password file

21. What is the ASM POWER_LIMIT?

Ans: This is the parameter that controls the number of Allocation units the ASM instance will try to rebalance at any given time. In ASM versions less than 11.2.0.3 the default value is 11 however it has been changed to unlimited in later versions.

22. What is a rolling upgrade?

Ans: A patch is considered rolling if it is can be applied to the cluster binaries without having to shut down the database in a RAC environment. All nodes in the cluster are patched in a rolling manner, one by one, with only the node which is being patched unavailable while all other instances open.

23. What are some of the RAC-specific parameters?

Ans: Some of the RAC parameters are:

1. CLUSTER_DATABASE
2. CLUSTER_DATABASE_INSTANCE
3. INSTANCE_TYPE (RDBMS or ASM)
4. ACTIVE_INSTANCE_COUNT
5. UNDO_MANAGEMENT

24. What is the future of the Oracle Grid?

Ans: The Grid software is becoming more and more capable of not just supporting HA for Oracle Databases but also other applications including Oracle’s applications. With 12c there are more features and functionality built-in and it is easier to deploy these pre-built solutions, available for common Oracle applications.

25. What components of the Grid should I back up?

Ans: The backups should include OLR, OCR, and ASM Metadata.

26. Is there an easy way to verify the inventory for all remote nodes?

Ans: You can run the OPATCH LSINVENTORY -ALL_NODES command from a single node to look at the inventory details for all nodes in the cluster.

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