Top 25 Oracle RAC Interview Questions and Answers in 2023

25 Oracle RAC Interview Questions & Answers

Did you clear your studies recently and are currently looking for a job? Or are you searching for a better salary or working environment? Whatever the case, these Oracle RAC interview questions and answers are for you. They will enhance your knowledge and help you to emerge as the best candidate. 

1. What Is Oracle RAC

Oracle Real Application Cluster (RAC) is a unique technology that offers software for high availability and clustering in an Oracle database environment. It permits multiple computer systems to access and run database software concurrently while having access to a single database, thus supporting clustering. The main objective of Oracle RAC is to support clustered databases in order to offer high availability, resilience, scalability, and performance of data at all levels.

2. What Is Data Guard In Oracle?

This is a configuration that maintains at least a single standby database of the main Oracle database. This means the primary Oracle database may have either a single or multiple standby databases. The entire configuration of all those databases is referred to as data guard. This configuration helps to ensure data integrity across the connected databases and the applications that use them.

3. What Is Split Brain In Oracle RAC?

Split Brain is used when describing a situation when multiple clustered nodes lose connectivity with each other but continue to function independently. For instance, they can acquire physical or logical resources independently. Each node functions under an incorrect assumption that other processes are not using the same resources or are no longer operational. 

4. What Is The Difference Between Crash Recovery And Instance Recovery?

Crash recovery refers to the recovery from crashes relating to all instances of an Oracle RAC database or single-instance database. On the other hand, instance recovery in an Oracle RAC database has to do with the recovery of a surviving instance from a failed instance. That said, the goal of these two types of recoveries is to restore data block changes that are in the cache of a failed instance. Both use online redo log files only and the recovery time is governed by various aspects including the number of dead instances.  

5. What Is Oracle Fail-Safe?

Every business expects its services and products to be available round-the-clock. But it is hard to find a system that offers 100% availability 24 hours every day for 365 days. Nonetheless, Oracle fail-safe helps to reduce the downtime of an Oracle database. It also cuts the downtime of other applications that run on Microsoft clusters. Oracle Fail Safe is a reliable and user-friendly application that is compatible with Microsoft Cluster Server (MSCS). It offers high availability on Microsoft clusters. Oracle Fail Safe works together with MSCS cluster applications to increase the availability of databases and applications running on a cluster. Whenever a cluster node suffers failure, the cluster software finds the surviving node and transfers its workload to it.

6. Tell Us Three Benefits Offered By Oracle Fail-Safe?

The first is that it makes resources and applications highly available. Together with MSCS, Oracle fail-safe works to enhance the availability of software and hardware resources. High availability helps to significantly reduce business downtime. The second benefit is the easiness of use. The process of configuring software can be complex considering the numerous components involved. But Oracle fail-safe is easy to install as well as use and administer. It is designed in a manner that simplifies software configuration in a cluster. The third advantage is that Oracle fail-safe is easy to integrate with other applications. When one desires to configure an application either to access databases or other software that are configured with Oracle fail-safe, very few changes are needed and sometimes none is required. 

7. Explain The Uses Of RAC

One of the ways real application clusters are used is to offer support to software where aspects like grouped level clustering and high availability are expected. They also help to detect any unwanted errors or results. In itself, RAC efficiently provides a very quick solution to all the problems detected. This is made possible by using auto-recovery from failures even before a user is notified about the problem. RAC ensures that the server that is charged with managing a database does not rely on just one point of failure. It accomplishes this by building as well as providing a fault tolerance mechanism. This ensures that the entire system does not go down when a single node becomes faulty. So, when one node goes down, other provided sources take over and ensure reliability. Another use is that RAC ensures the state is recovered easily and quickly after a failure has occurred. 

8. What Is A VIP Used For In RAC?

A VIP in RAC is an alternative virtual IP address that is assigned to each node in a cluster. It is very essential in communicating about the failure of a node. In other words, when a node fails, the alternative virtual IP address proceeds to the surviving node and sends a message to the application that the node has failed. If a VIP is absent, the application will have to wait until the TCP timeout to discover the session is not live because of a node failure.

9. What Is OCLUMON Used For In Cluster Health Monitor?

OCLUMON is used to store the metrics of the operating system in the cluster health monitor (CHM) repository. It keeps data regarding the memory, CPU, network, process, and other information regarding the operating system. This data is kept for various purposes including troubleshooting as well as identifying any issues related to the cluster. OCLUMON stores the data in a master repository and replicates it to a standby repository that is located on a different node.

10. What Components Are Needed To Manage Oracle RAC Database?

To configure and manage servers easily Oracle RAC employs a single system. Oracle RAC offers a database for the configured and installed applications from a single location. It is this strategy that enables it to manage the servers with ease. Several components are needed to help Oracle RAC accomplish its management role. One of them is the Oracle Universal Installer that helps to manage the database related to the cluster. This universal installer also provides enterprise-level configuration. Another component is the Database Configuration Assistant, which manages the database as well as its related services and functionality. The other component is the database Upgrade Assistant, a tool that helps to upgrade the database whenever such an operation is needed on the server.

11. Explain Why The Cluster Verification Utility Is So Essential In Oracle RAC

In the Oracle Grid, the Cluster Verification Utility is a tool, which helps to do away with the errors that are associated with the validation steps. It helps with the verification of changes being made in the system or configuration files. This tool is used when verifying the pre-requisites of a system that are associated with Oracle and Oracle databases. The Cluster Verification Utility is also employed when validating the configuration input to make sure that everything goes well during installation. This tool may also be used together with the command-line interface. In case this tool fails during verification, there are some fix-up scripts available that automatically fix errors.

12. What Is Meant By Load Balancing Advisory?

Load Balancing Advisory refers to the process through which applications and resources’ load are managed successfully across the servers. It plays the role of monitoring the workload of ongoing activities relating to the instances and clusters being forwarded to the server. The task of managing activity workload is simplified by providing a percentage value that shows the entire workload of all instances. It also flags any instance whenever something unusual is identified. Load Balancing Advisory also helps to maintain loads from servers as well as distribute them equally across other functioning servers.

13. What Purpose Does Oracle Local Repository Play?

Oracle Local Repository (OLR) is a storage of information and it permits the starting up of cluster processes. It allows these processes while the oracle cluster registry (OCR) is in the automatic storage management (ASM) storage system. A copy of the OCR that is stored in OLR is required during the starting up the process of the Grid processes, which ought to run to make the ASM file system available.

14. What Are Clustered File Systems?

These are file systems that operate on several storage servers and they can be accessed as well as be managed as one system. All members in a cluster can access these file systems simultaneously. A clustered file system brings together and shares available capacity on storage networks. Ultimately, the storage utilization rate is increased and this translates to better performance. Most file systems have a volume manager that enables the system admin to allocate capacity as required. These systems control the way a node accesses shared storage. This control prevents an instance where multiple nodes create overlapping writes.

15. What Is Oracle Cluster Registry Used For?

The Oracle Cluster Registry or OCR is used to manage a cluster and Real Application Clusters configuration. It holds cluster and database configuration information for Cluster Ready Service and Real Application Clusters. The OCR file is often shared and is situated in a cluster file system. When installing cluster-ready services, the OCR is initiated automatically by the Oracle Universal Installer. If an administrator creates multiple databases on a cluster, all of them share a single Oracle Cluster Registry. 

16. Explain The Use Of Cluster Interconnect In Oracle

Cluster interconnect refers to the physical configuration of devices and it is implemented to help transfer data service communications and cluster-private communications across different cluster nodes. Thus, it is only cluster nodes that can be linked to the cluster interconnect. The three hardware components that make up a cluster interconnect are cables, junctions, and adapters. Cables consist of the physical connections that are installed between adapters or a junction and an adapter. Junctions are the switches located outside cluster nodes.

17. How Can You Maximize The Performance Of A Cluster Interconnect?

The easiest and fastest way to maximize the efficiency and speed of an interconnect is to set the User Datagram Protocol (UDP) buffers to the correct values. That way, you can have the fastest possible network. In an Oracle environment, the interconnect serves as your cluster backbone. Faster transfer of messages and data among instances requires a reliable and highly performing interconnect. Setting the cluster to interconnect correctly will help to easily achieve the desired reliability and efficiency.

18. What Are Some Of The Measurements Involved In A Cluster Interconnect Test?

One of the measurements made during this test is cluster interconnect percentage, which shows if a cluster interconnect is available or unavailable on a node. Logon rate is another assessment parameter that is used to indicate the rate at which user logins have happened on a node. The other measurement is processes utilization, which indicates the processes that are running on a cluster node. Session utilization is another measurement parameter that shows the sessions that are active on a node at a particular time.

19. What Procedure Would You Follow To Restore The Oracle Cluster Registry On Windows-Based Systems?

I would begin by shutting down the nodes in the Oracle RAC database but leaving just one node. Next, I would proceed to stop OCR clients/services and thereby prevent them from utilizing the Service Control Panel. These OCR clients include Oracle cluster volume and earned value management services. Then, using the show backup command, I would find out the recent backups that have been performed. This would be followed by the execution of the restore process using the OCR backup file. Lastly, I would start all the stopped OCR services and resume operations after restarting all instances as well.

20. What Is Meant By Voting Disk In Oracle RAC?

In Oracle RAC, a voting disk is a file, which helps to manage information about node membership. All the nodes in a cluster record their running information on the voting disk. This disk also keeps a record of all the active nodes. In other words, voting disks can be likened to attendance registers where nodes confirm that they are active. If the disk does not get updated within the expected time, the usual conclusion is that the node is unhealthy and the next action may be to restart it in order to protect the database.

21. What Benefits Does Oracle RAC Offer Its Users?

Oracle provides businesses of all sizes and shapes with Real Application Clusters (RAC). Oracle RAC offers high performance, great pricing, scalability, and high user concurrency. It is very reliable because of its around-the-clock availability. Also because of the structure of RAC, organizations with critical databases consider it as the best solution.

22. What Is Automatic Storage Management?

Automatic Storage Management or ASM is a feature in an Oracle database that provides a simplified storage management process to Oracle customers. This storage management process is consistent across storage platforms and servers. ASM helps customers to manage storage as small storage pools known as ASM disk groups. These disk groups offer an easy and convenient way to consolidate storage as well as simplify administrative tasks. Files related to a database are assigned to a group and ASM manages data organization and layout to ensure optimal performance. ASM also safeguards ASM disk groups from storage hardware failures.

23. State The Main Benefits Of ASM

ASM offers many benefits and one of the key ones is simplifying and automating storage management. It also increases storage agility and utilization. ASM offers support to the database when the server crashes. Besides, it delivers predictable scalability, availability, and performance. It offers the underlying storage management for the Automatic Storage Management cluster file system. This feature offers centralized storage for the data that is outside the database. Oracle ASM helps to cut the administrative overhead involved in managing database storage. This is achieved by combining data storage into small disk groups. 

24. What Does Oracle RAC Family Of Solutions Mean?

The Oracle RAC Family of Solutions is a collection of features and products, which licensed Oracle RAC. Each of the solutions complements or enhances the core Oracle RAC offering. This is achieved by making sure that there is better and high scalability and performance and also by simplifying and automating daily operations. 

25. What File Types Are Supported By Oracle ASM?

Oracle ASM works with most of the file types needed by the Oracle database. These include archive log files, audit spill files, persistent initialization parameter files, data file backup files, autologin software Keystore, control files, data files, and flash files. It also supports redo log files, voting files, temporary files, oracle cluster registry files, cross-platform transportable data files, and change tracking files.


With these questions, you are set to prepare adequately for your next Oracle RAC interview. You simply need to study and practice them. When answering interview questions, be audible and show confidence to win the trust of your interviewers. Also, ensure to wear decently and arrive early for the interview.