Answer / oracle

RAC stands for REAL APPLICATION CLUSTER, it is and advance future from oracle
10g
Oracle RAC allows multiple computers to run the Oracle RDBMS software
simultaneously while accessing a single database, thus providing a clustered
database.

Since Oracle RAC allows multiple computers to access a single database
simultaneously, it addresses several areas of database management. These
areas include:
fault tolerance
load balancing
scalability

Answer / sumit kumar

RAC stands for Real Application Clusters. It allows
multiple nodes in a clustered system to mount and open a
single database that resides on shared disk storage. Should
a single system fail (node), the database service will
still be available on the remaining nodes.

A non-RAC database is only available on a single system. If
that system fails, the database service will be down
(single point of failure).

Answer / waseem

RAC is Cluster software available from Oracle. This is
available 10g onwards.

In this Cluster environment we can have multiple instances
running with a single database. Users are connected to
different instances. Availability and load balancing is the
main purpose behind Oracle RAC.

VD (Voting Disk) and OCR (Oracle Cluster Registry) are the
components of RAC. VD is similar to control file and OCR has
all the registered services to start the cluster.

The connection of user could be established on any node but
later depending on the number of users connections
established and the number of instances(nodes) available the
load of all the established connections is balanced across
the Cluster.

The first node created in the Cluster is the Master Node and
all other nodes in the Cluster nbehaves like Slaves.

If any slave node fails to communicate with Master node,
internally the failed node is rebooted by the Master node by
writing a kill block into VD. If the Master node fails, then
any of the existing node responding first will become the
Master node and reboots the failed node.

Daemons checks for the availability of VD,nodes and OCR and
cluster is started.

We can add nodes to the existing cluster from any exiting
node which is already a part of the cluster. We can also
delete a node from the cluster by stopping all the services
of that node from the CRS inventory and home.

We can have multiplexed copies of VD and OCR. VD (Min 1 and
Max 310....OCR(Min 1, Max 2).

We can take backup of VD and OCR with the help of dd (disk
dump). For OCR we can also perform logical backup using
export utility.

Note: Use ASM (logical location for physical diskgroups) for
the best performance).
Create ASM instance for each node.

Answer / brajendra arzare

Oracle RAC allows multiple computers to run the Oracle
RDBMS software simultaneously while accessing a single
database, thus providing a clustered database.
In a non-RAC Oracle database, a single instance
accesses a single database. Where the "database" consists
of a collection of data files, control files, and redo logs
located on disk; the "instance" comprises the collection of
Oracle-related memory and operating system processes that
run on a computer system.

In an Oracle RAC environment, two or more computers (each
with an instance) concurrently access a single database.
This allows an application or user to connect to either
computer and have access to a single coordinated set of
data.

Answer / yogesh a d

RAC is the Oracle's Technology to protect the RDBMS from instance failure only and not the media failure. To overcome the media failure there is Data Guard technology of Oracle.

RAC provides Cluster environment to database, in this single database can be managed by number of instances. So that if one of the instance fails the database will not shutdown.

Answer / harry dubai

In simple terminology...RAC is a Single database with
multiple instances.

RAC is used for load balancing and high availablity in case
of instance failure or media failure.

Answer / s raj

Hi,

tell me how to trableshoot in RAC and log file details and
please provide me interview qucations

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