Overview of Oracle Data Guard Data Replication

This section provides an overview of the integration of Oracle Data Guard with Sun Cluster Geographic Edition and highlights the differences between support for Oracle Data Guard and other data replication products, such as Sun StorageTek^TM Availability Suite software, Hitachi TrueCopy, and EMC SRDF.

Oracle Data Guard Shadow Resource Groups

You can add an Oracle Data Guard Broker configuration that is controlled by the Oracle Data Guard software to a protection group. The Sun Cluster Geographic Edition software creates a shadow RAC server proxy resource group for each Oracle Data Guard Broker configuration. The name of a shadow resource group conforms to the following format:

ODGconfigurationname-rac-proxy-svr-shadow-rg

For example, an Oracle Data Guard Broker configuration named sales that is controlled by the Oracle Data Guard software has a shadow RAC server proxy resource group named sales-rac-proxy-svr-shadow-rg. If, however, the configuration name contains one or more periods (.), the periods are converted to underscore characters (_) to construct the resource group name. Consequently, the configuration name mysales.com has a shadow resource group named mysales_com -rac-proxy-svr-shadow-rg.

The shadow RAC server proxy resource group “shadows” the real RAC server proxy resource group that you created to manage and monitor the Oracle RAC databases that are under the control of Sun Cluster software.

Each shadow resource group contains a single resource: a SUNW.gds resource whose probe script reflects the status of the RAC server proxy resource group. The name of this resource conforms to the following format:

ODGconfigurationname-rac-proxy-svr-shadow-rs

For more information about RAC server proxy resource groups, see Sun Cluster Data Service for Oracle RAC Guide for Solaris OS.

A shadow RAC server proxy resource group is required because, unlike other Sun Cluster Geographic Edition replication products, the Oracle Data Guard software is an integral part of the Oracle RAC software. Oracle Data Guard requires the Oracle RAC software to be running and the databases started to replicate its data.

Consequently, putting the real RAC server proxy resource group under Sun Cluster Geographic Edition control would result in the Oracle RAC database's being shut down on the standby cluster. In contrast, the shadow RAC server proxy resource group can be placed under the control of Sun Cluster Geographic Edition. You can do so without disrupting the data replication process while still allowing the configuration to conform to the usual Sun Cluster Geographic Edition structure for managing application resource groups.

The state of the shadow RAC server proxy resource group indicates whether the database that is monitored and controlled by the RAC server proxy resource group is the primary or the standby cluster. In other words, this state indicates whether the database is online on the primary cluster and unmanaged on the standby cluster. Furthermore, the status of the shadow RAC server proxy resource reflects both the status of the RAC server proxy resource and whether the database is the primary or the standby.

Oracle Data Guard Replication Resource Groups

When an Oracle Data Guard Broker configuration that is controlling the Oracle Data Guard software is added to a protection group, the Sun Cluster Geographic Edition software creates a special replication resource for the specific Oracle Data Guard Broker configuration in the replication resource group. By monitoring these replication resource groups, the Sun Cluster Geographic Edition software is able to monitor the overall status of replication. One replication resource group with one replication resource for each Oracle Data Guard Broker configuration is created for each protection group.

The name of the replication resource group conforms to the following format:

ODGProtectiongroupName-odg-rep-rg.

The replication resource in the replication resource group monitors the replication status of the Oracle Data Guard Broker configuration on the local cluster, which is reported by the Oracle Data Guard Broker software.

The name of the replication resource conforms to the following format:

ODGBrokerConfigurationName-odg-rep-rs.

In Oracle Data Guard, a data replication resource is enabled when the protection group is activated in the cluster. Consequently, in Oracle Data Guard, in a cluster in which the protection group is deactivated, the data replication status appears as unknown.