These Oracle RAC Interview Questions have been designed specially to get you acquainted with the nature of questions you may encounter during your interview for the subject of Oracle RAC . As per my experience good interviewers hardly plan to ask any particular question during your interview, normally questions start with some basic concept of the subject and later they continue based on further discussion and what you answer.we are going to cover top 100 Oracle RAC Interview questions along with their detailed answers. We will be covering Oracle RAC scenario based interview questions, Oracle RAC interview questions for freshers as well as Oracle RAC interview questions and answers for experienced.
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).
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.
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.
It is a private network which 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.
One of the ways is to look at the database alert log for the time period when the database was started up.
6) What methods are available to keep the time synchronized on all nodes in the cluster?
Either the Network Time Protocol(NTP) can be configured or in 11gr2, Cluster Time Synchronization Service (CTSS) can be used.
You can use either the logical or the physical OCR backup copy to restore the Repository.
12) What happens if you keep split brain syndrome in RAC unresolved? How it can be resolved?
If you keep split brain syndrome unresolved, then there would be data integrity issue. The blocks changed in one instance will not be locked and could be over-written by another instance. It is resolved by using the voting disk, it will decide which node(s) will survive and which node(s) will be evicted.
ORL stands for Oracle Local Repository (OLR). It consists of information which enables the cluster programs to initiate with the OCR in the ASM Storage. Until the grid process are started, the ASM file is unavailable. In such case, a local copy of the data of the OCR is required, that is stored in OLR.
The alternate to virtual IP address is called VIP. Every node of the cluster is mapped with VIP and therefore in case of any node failure the VIP notifies the application about the node being down and itself switches towards the surviving node. In the absence of VIP, the TCP timeout would be encountered by the application. This TCP timeout then would notify a dead session as a result of the failure.
OLR or popularly known as Oracle Local Repository consists of details related to cluster and the processes related to it when the OCR is in the ASM system. The grid process takes time to start and in the meanwhile ASM system will also be unavailable and therefore an OCR local copy is booted which is eventually stored inside OLR.
A rolling patch refers to the cluster binaries being applied on the up and running databases of RAC environment. The cluster nodes are rolled one after another where the patched node is unavailable whereas all other instances are in open state.
This is the basic Oracle RAC Interview Question asked in an interview. The combination of data blocks coming straight from remote database caches and getting shipped to the local nodes so that the requirements for doing a transaction such as a DDL or a DML can be fulfilled.
RAC or Real Application Clusters are used to support all the software where aspects such as high availability and grouped level of clustering are expected. Other uses of RAC are:
Md_backup is the command which can be used to take ASM metadata backup. It is also used to restore the disk group based configurations if a storage loss for ASM disk group is encountered.
26)Suppose your remote nodes have some inventory and you are given the task of identifying and verifying them. How will you do that?
“Opatch Inventory-all_nodes” is the command which will ensure that you are able to access the data of all the remotely located nodes by just a single node.
21)How do you find out what object has its blocks being shipped across the instance the most?
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.
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.
25)What would be the possible performance impact in a cluster if a less powerful node (e.g. slower CPU’s) is added to the cluster?
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.
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.
You can use md_backup to restore the ASM diskgroup configuration in-case of ASM diskgroup storage loss.
This is the parameter which 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.
Oracle RAC enables you to cluster Oracle databases.Oracle RAC uses Oracle Clusterware for the infrastructure to bind multiple servers so they operate as a single system.Oracle Clusterware is a portable cluster management solution that is integrated with Oracle Database.
16) Mention where does the Clusterware write when there is a network or storage issue?
When there is a network or storage issue the network ping failure is written in $CRS_HOME/log
Part 1 – Oracle RAC Interview Questions (Basic)
This first part covers basic Oracle RAC Interview Questions and Answers
Answer: It is related with the miscommunication among nodes of a cluster. Those database nodes then continue their processing and make relevant changes in their data blocks on their own. In case multiple instances are responsible for modifying one block, the data blocks are not able to synchronize among themselves and those writes will be done by others for the same block. This entire process is called the split brain.
Answer: The alternate to virtual IP address is called VIP. Every node of the cluster is mapped with VIP and therefore in case of any node failure the VIP notifies the application about the node being down and itself switches towards the surviving node. In the absence of VIP, the TCP timeout would be encountered by the application. This TCP timeout then would notify a dead session as a result of the failure.
OLR or popularly known as Oracle Local Repository consists of details related to cluster and the processes related to it when the OCR is in the ASM system. The grid process takes time to start and in the meanwhile ASM system will also be unavailable and therefore an OCR local copy is booted which is eventually stored inside OLR.
Let us move to the next Oracle RAC Interview Questions.
Answer: A rolling patch refers to the cluster binaries being applied on the up and running databases of RAC environment. The cluster nodes are rolled one after another where the patched node is unavailable whereas all other instances are in open state.
Answer: This is the basic Oracle RAC Interview Question asked in an interview. The combination of data blocks coming straight from remote database caches and getting shipped to the local nodes so that the requirements for doing a transaction such as a DDL or a DML can be fulfilled.
Answer: RAC or Real Application Clusters are used to support all the software where aspects such as high availability and grouped level of clustering are expected. Other uses of RAC are:
Introduction to Oracle RAC Interview Questions and Answers
When you talk about computing related to database, Oracle RAC (Real Application Clusters) provides and support software related to high availability and clustering within the Oracle environments. By using Oracle RAC, a number of computers can access Relational Database Management System of Oracle at the same time even when they are using only a single database, thereby supporting clustering. The interconnect is used to connect multiple instances among themselves and they all work in perfect synchronization while trying to access the data. In this post, we are going to study some of the Oracle RAC Interview Questions.
Now, if you are looking for a job which is related to Oracle RAC then you need to prepare for the 2023 Oracle RAC Interview Questions. It is true that every interview is different as per the different job profiles. Here, we have prepared the important Oracle RAC Interview Questions and Answers which will help you get success in your interview.
In this 2023 Oracle RAC Interview Questions article, we shall present 10 most important and frequently used Oracle RAC interview questions. These questions are divided into two parts are as follows: