||Oracle Tips by Burleson
10g Grid Computing
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
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 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.
The above text is
an excerpt from:
Oracle 10g Grid & Real Application
Computing with RAC
by Mike Ault, Madhu Tumma
Oracle Consulting Services
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