Oracle Tips by Burleson

10g Grid Computing with RAC
Real Application Cluster Architecture

Cluster Ready Services - CRS

The OUI installs CRS on each node on which the OUI detects that vendor clusterware is running. In addition, the CRS home is distinct from the RAC-enabled Oracle home. The CRS home can be shared either by one or more nodes, or by private to each node, depending on the settings when you run the OUI. When vendor clusterware is present, CRS interacts with the vendor clusterware to coordinate cluster membership information.

For Oracle10g on Linux and Windows-based platforms, CRS co-exists with but does not inter-operate with vendor clusterware. You may use vendor clusterware for all UNIX-based operating systems except Linux.

The Oracle Cluster Registry (OCR) contains cluster and database configuration information for Real Application Clusters Cluster Ready Services (CRS), including the list of nodes in the cluster database, the CRS application, resource profiles, and the authorizations for the Event Manager (EVM). The OCR can reside in a file on a cluster file system or on a shared raw device. When you install Real Application Clusters, you specify the location of the OCR.

CRS helps to package a set of application work under CRS control and access the RAC database. The application resource profile defines the resources with which you manage the RAC.

Prior to the 10g release, the cluster manager implementations on some platforms were referred to as "Cluster Manager". In Oracle10g, Cluster Synchronization Services (CSS) is the cluster manager on all platforms. The Oracle Cluster Synchronization Service Daemon (OCSSD) performs this function on UNIX-based platforms. On Windows-based platforms, the OracleCSService, OracleCRService, and OracleEVMService provides the cluster manager functionality.

CRS Features

CRS is required for installing the Oracle 10g RAC system. If you have a vendor provided Cluster Software running, CRS can be either run on top of that. The vendor supplied clusterware is however optional. 

The CRS software is installed in the cluster with its own set of binaries. The CRS Home and Oracle Home are in different locations. CRS software installation uses the two shared disk locations or files which are the Voting Disk and OCR file.

Installation of CRS configures the Virtual IP interface. Virtual IP is associated with defined Workload Service

CRS resources can also be managed by the srvctl utility. CRS has many daemon processes. They are as follows:

CRDS – The CRS Daemon is the main background process for managing the HA operation of the service. Basically, it manages the application resources defined within the cluster. It also maintains the configuration profiles stored in the Oracle Configuration Repository.

OCSSD – This process is associated with the ASM (Automatic Storage Management) instance. This daemon is spawned to manage the shared access of the disk devices to the clustered nodes. It manages the basic cluster locking, understands the nodes and its membership status.

EVMD – This is event management logger. It monitors the message flow between the nodes and logs the relevant event information to the log files. 

Oracle Consulting Services

Burleson Oracle Consulting offers Senior Oracle consultants which are available for all areas of Oracle support.  Common Oracle consulting support activities include short-term Oracle tuning, Oracle database troubleshooting, Oracle9i and Oracle10g migration, Oracle9iAS App Server consulting, Oracle design reviews and Oracle requirements evaluation support. Oracle support and Oracle consulting services are priced by the hour, so you only pay for what you need. These one-time Oracle consulting services commonly include:

• Answering questions from your Oracle DBA technical staff

• Repairing down production Oracle database systems

• One-time Oracle tuning evaluation

• Guru support for your Oracle DBA

• Installation of Oracle application packages

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