Thursday, July 16, 2009

Oracle Database Administratron

Oracle Real Application Clusters (RAC):

Oracle introduced Oracle Parallel Server (OPS) in Oracle version 6.0 and is available till version 8i.

Later on Oracle introduced Oracle Real Application Clusters (RAC) in 9.1 version. It's cache fusion technology fully enhanced in Oracle 9.2( 9i Release 2).
Oracle RAC was further matured in 10.1 and 10.2.

Oracle introduced it's clustering software for Linux to support RAC in 9i, which was further enhanced in 10.1 and 10.2.

In Oracle 9i , Oracle's clustering software was known as Oracle Cluster Manager (oracm).
In Oracle 10.1 Oracle further renamed it to Cluster Ready Services (CRS).
In Oracle 10.2 Oracle further renamed it to Oracle Clusterware, which is mandatory in Linux RAC environment, otherwise will not be supported by Oracle.

For RAC database installation, it is necessary to install Oracle Clusterware before installing Oracle RDBMS. To install Oracle Clusterware separate home directory needs to be created called CRS_HOME generally under ORACLE_BASE directory.

Oracle Clusterware contains following 5 components:
3 Daemons:
1. Oracle Cluster Synchronization Services Daemon (OCSSD): which is being used to cluster node membership.
2. Cluster Ready Services Daemon (CRSD): which performs management operations and
recovery incase of node or instance failure in RAC.
3. Event Manager Daemon (EVMD): which provides event notification among cluster nodes.

2 Files:
4. Oracle Cluster Registry (OCR)
5. Voting Disk ( in 9i was known as Quaram disk).