Support of Oracle RAC ASM with SGeRAC, January 2008

HP Availability Clusters Solutions Lab 1/25/2008 Page 5

Clustered ASM Environment

In an Oracle Clusterware environment, the individual ASM instances, one per node, cooperate to

offer shared disk group access across the cluster. One or more RAC databases may be configured in

the cluster, using the shared disk groups. Single instance databases may also be configured to use the

shared disk groups but Oracle Clusterware does not provide built-in management and monitoring for

them.

The ASM instances are under the control of Oracle Clusterware. Oracle Clusterware manages the

start, stop and health check functions for the ASM instances just as it does for RAC database

instances. Oracle Clusterware also ensures that the RAC database instances and the ASM instance

start and shutdown in the proper order (that is, the ASM instance starts up before the database

instances and shuts down after the database instances). Figure 3 shows the clustered ASM

environment.

Figure 3. RAC ASM Environment

The ASM instances communicate with each other to maintain the consistency of the metadata of the

disk groups they are managing.

ASM

Instance

Get DB File

Extent

Maps

RAC DB

Instances

Oracle

Clusterware

- Provide Membership

- Start/Stop/Check Instance

- ..

ASM

Instance

RAC DB

Instances

Oracle

Clusterware

RAC Cache Fusion communication

ASM-ASM synchronization

Heartbeat,

CRS-CRS communication

Node

Node 1

Oracle DBs in ASM Disk Groups

Read/Write DB Files

-Read/Write Disk Group Headers

-Rebalance Disk Group Data