Oracle Database Tips by Donald Burleson

Oracle10g Grid Computing with RAC
Chapter 8 - RAC Administration

Oracle Database 10g ASM (Automated Storage Management)

Automatic Storage Management's native mirroring mechanism is an option that can be set when creating a disk group. You can specify the redundancy protection for that group, and if you prefer to use an external mirroring system or you have no need for fault-tolerance, you can set the redundancy to external, in which case ASM will not mirror at all. Unless otherwise specified, redundancy defaults to normal, in which case ASM mirrors each 1 MB extent. For the highest level of fault tolerance, you can specify high redundancy, which provides three-way mirroring.

Server Control Utility

To manage the RAC database and its instances, Oracle provided a utility called the Server Control Utility (SRVCTL) in version 9i. This replaced the earlier utility 'opsctl' which was used in the parallel server.

The Server Control Utility is a single point of control between the Oracle Intelligent agent and each node in the RAC system. The SRVCTL communicates with the global daemon service (GSD) and resides on each of the nodes. The SRVCTL gathers information from the database and instances and acts as an intermediary between nodes and the Oracle Intelligent agent.

When you use the SRVCTL to perform configuration operations on your cluster, the SRVCTL stores configuration data in the Server Management (SRVM) configuration repository. The SRVM includes all the components of Enterprise Manager such as the Intelligent Agent, the Server Control Utility (SRVCTL), and the Global Services Daemon. Thus, the SRVCTL is one of the SRVM Instance Management Utilities. The SRVCTL uses SQL*Plus internally to perform stop and start activities on each node.