VCS Framework and Service Groups

Veritas Cluster Server (VCS) is the overall framework that controls the Oracle RAC database and other required essential resources such as shared storage and listener. VCS acts as a director of operations. All activities within Oracle RAC and its infrastructure are managed with the VCS framework.

VCS manages its resources in the form of a group. A collection of resources of different types for a given application or task is called a service group. Service groups act as containers for all the necessary components and resources of an application. They are defined and managed as a single unit. A service group definition typically consists of:

• The keyword ‘group’ (in the configuration file).

• Name of the service group.

• The service group’s attribute values (enclosed in parentheses). VCS predefine service group attributes.

• The definition of service group resources. (with attributes / values)

• The dependencies between the service group resources.

In Veritas DBE/AC, two service groups are defined to support and control the RAC database. One service group deals with the volume manager resources, file system resources, listener resources, and shared Oracle Home directory. The other service group deals with the Oracle database and supports CVM and CFS resources. These two groups are specified to be parallel groups as shown in Fig 6.9. VCS does not attempt to migrate a ‘failed service group’.

Fig 6.9 Veritas Service Groups for RAC

DBEAC provides agents to operate and control all resources. Agents are the VCS processes that bring resources online and take them offline. Resources are brought online and offline in an orderly manner based on the resource dependency. Agents also monitor resources and report any state changes to VCS.

Some of the agents are specific to advance clusters including CVMCluster, CVMVoldg and CFSMount. The Agents stop and start the resources as required. The VCS implementation for Oracle Failover clusters does not include these agents.