Overview of Oracle Data Guard Data Replication

This section provides an overview of the integration of Oracle Data Guard with Geographic Edition and highlights the differences between support for Oracle Data Guard and other data replication products, such as StorageTek Availability Suite software, Hitachi TrueCopy or Universal Replicator, and EMC Symmetrix Remote Data Facility (EMC SRDF).

Oracle Data Guard Shadow Resource Groups

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

The name of a shadow resource group conforms to the following format:

ODGconfigurationname-rac-proxy-svr-shadow-rg

This format applies regardless of which data service is configured for the Oracle Database software — Oracle Solaris Cluster Support for Oracle Real Application Clusters (Oracle RAC) or Oracle Solaris Cluster HA for Oracle (HA for Oracle).

For example, an Oracle RAC database in an Oracle Data Guard Broker configuration named sales has a shadow Oracle database-server 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.

Similarly, an HA for Oracle database in an Oracle Data Guard Broker configuration named inventory that is controlled by the Oracle Data Guard software has a shadow Oracle database-server resource group named inventory-rac-proxy-svr-shadow-rg.

The requirements for consistent name construction are two-fold. First, this allows a shadow resource group to be added to a protection group even when one cluster uses Oracle RAC and the other uses HA for Oracle. The second reason is that is that this format is required for backward compatibility.

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

• HA for Oracle – ODGconfigurationname-oracle-svr-shadow-rs

• Oracle RAC – ODGconfigurationname-rac-proxy-svr-shadow-rs

For more information about Oracle database-server resource groups, see Oracle Solaris Cluster Data Service for Oracle Real Application Clusters Guide and Oracle Solaris Cluster Data Service for Oracle Guide.

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

Consequently, putting the real Oracle database-server resource group under Geographic Edition control would result in the Oracle database being shut down on the standby cluster. In contrast, the shadow Oracle database-server resource group can be placed under the control of Geographic Edition. You can do so without disrupting the data replication process while still allowing the configuration to conform to the usual Geographic Edition structure for managing application resource groups. In addition, putting the shadow resource groups under Geographic Edition control enables you to declare on the shadow resource-group affinities and other relationships with other resource groups. These other resource groups can then also be controlled by Geographic Edition.

The state of the shadow Oracle database-server resource group indicates whether the database that is monitored and controlled by the Oracle database-server 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:

• If the shadow Oracle database-server resource group is online, its cluster is the primary cluster for that Oracle database, which is represented by the resource in the actual Oracle database-server resource group.

• If the shadow Oracle database-server resource group is offline and unmanaged, its cluster is the standby for that Oracle database.

Furthermore, the status of the shadow Oracle database-server resource reflects both the status of the Oracle database-server 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 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 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 replication resource also checks the accessibility of the configuration through the remote service name, to ensure that the username and password information, or the Oracle wallet if used, is correctly configured.

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

ODGBrokerConfigurationName-odg-rep-rs.