Top 19 Oracle Real Application Clusters Interview Questions You Must Prepare 23.Jan.2025

• OCFS (Release 1 or 2)
• ASM
• raw devices
• third party cluster file system such as GPFS or Veritas

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 traction (DML, Query of Data Dictionary).

• Oracle Real Application (RAC) provides the interaction of executable file with the Oracle database.
• It allows the running of any packaged or custom built application with the Oracle database that is running on a server pool.
• It provides very high level of availability, flexibility and scalability to run the application and store it to the database.
• It creates the database such that if the pool fails then the database is continued to run from the remaining servers and the load can be distributed.
• It makes it easier for the administrator to maintain many servers at the same time by load-balancing techniques and providing provision to add more and more servers when the load increases.

There are two types of connection load-balancing: server-side load balancing and client-side load balancing.

• The Hardware Architecture of the Oracle RAC clusters provides a shared architecture with the server pools and allows all the storage devices to be shared.
• Hardware Architecture supports different types of storage networks like Network attached storage (NAS), Storage Area Network (SAN) and SCSI disks.
• Hardware architecture is such that it provides appropriate choices for the storage pools and system that provides scalability and flexibility to the overall system.
• The architecture should contain the input and output for the application that need to be developed and then the system can have more scalability.
• Hardware architecture supports more application to be added in the server pool and allows better integration of services.

The Clusterware is installed on each node (on an Oracle Home) and on the shared disks (the voting disks and the CSR file).

• GSD runs on each node and is not an Oracle background process.
• This process performs administrative tasks, such as startup and shutdown, based on the requests from different clients, such as DBCA and enterprise manager.

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.

Oracle Clusterware is used to manage high-availability operations in a cluster. Anything that Oracle Clusterware manages is known as a CRS resource. Some examples of CRS resources are database, an instance, a service, a listener, a VIP address, an application process etc.

• Oracle RAC requires an active connection of the network to the LAN (Local Area Network) so that the database server can be found and connected.
• The database server is further having connections with application servers that store the applications and allow user to trfer their data.
• The connection is required with the server pool so that the trfer of services and applications can be done on demand basis.
• The interconnection between the networks is really important as it has to maintain the overall flow of the pools and the resources.
• Oracle RAC provides support to redundant interconnects relatively and it provides an overall infrastructure solution.
• The load balancing and inter-node messaging can be handled more carefully when the networks or the servers are interconnected to each other.

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.

RAC cluster is a database with a shared cache architecture that overcomes the limitations of traditional shared nothing and shared disk approaches.

It is a key component of Oracle's private cloud architecture.

ACMS ensures global updates to System Global Area (SGA) in a RAC set up.

• Rolling upgrade refers to the software upgrading while database is still functional without bringing the database down for upgrade.
• This is the new feature of Oracle 11g.

Oracle Flex ASM instance when fails on a particular node, then the Oracle Flex ASM instance is passed over to another node in the cluster.

• The file system and volume management in Oracle RAC should know about the architecture that is being used and it should be aware of the clusters that are involved in it. 
• Oracle supports automatic storage management that automates the storing of files and setup the communication in between the databases storage pools. 
• Oracle supports the high performance of the input and output of the storage subsystem by providing easy tools to use to maximize it.
• They provide a way to balance the load across the available resources that allows the correct optimization of the file system and volume management. 
• Oracle RAC provides dynamic volume manager and it has a file system that contains the information of the cluster file system as well. 
• The cluster file system in oracle is called as (OCFS) and it has the connection with the databases that provide raw devices and command line features.

• ACFS provides an Oracle Home shared file system or a general purpose clustered file system on ASM storage.
• It needs ASM Dynamic Volume Manager (ADVM) to communicate to the operating system.

The background processes required for RAC are given as follows:

• ACMS – Atomic Controlfile to Memory Service
• LMON – Global Enqueue Service Monitor
• LMD – Global Enqueue Service Daemon
• LMS – Global Cache Service Process
• LCK0 – Instance Enqueue Process
• RMSn – Oracle RAC Management Processes
• RSMN – Remote Slave Monitor

The base software is installed on each node of the cluster and the database storage on the shared disks.