For SADTA, a Site Controller Package must be configured to provide robust site failover semantics for a site aware disaster tolerant RAC database. The Site Controller Package starts the configured local RAC MNP stack packages on the site where it is started. The Site Controller Package monitors the started RAC MNP stack packages. When these packages fail, the Site Controller Package fails over to the remote site. As part of its startup on the remote site node during failover, the Site Controller Package prepares the replicated data storage and runs the passive RAC MNP stack packages in the remote site ensuring disaster tolerance for the database.
Since a disaster tolerant RAC database has two identical but independent RAC databases configured over the replicated storage in a Metrocluster, it is important to prevent packages of both sites RAC MNP stacks to be up and running simultaneously. If the packages of the redundant stack at both sites are running simultaneously, it leads to data corruption. SADTA provides a Site Safety Latch mechanism at the site nodes that prevents inadvertent simultaneous direct startup of the RAC MNP stack packages at both sites.
Multiple site aware disaster tolerant RAC databases can be configured in a Metrocluster. Figure
Figure 60 Sample Configuration
Multiple RAC databases can be configured using a separate Site Controller Package infrastructure for each RAC database. Each RAC database must have its own Site Controller Package, Site Safety Latch, RAC MNP package stack, and replication disk group in the Metrocluster. The
To add another RAC database to an existing Metrocluster, two replicas of the RAC database and the RAC MNP stack packages on both sites, in a separate Site Controller Package, must be configured.
Because the SADTA configuration requires two replicas of the RAC database configuration, the Oracle Network and Services must be configured accordingly for the disaster tolerant database clients to automatically reconnect to the new active site after a site failover is complete. For more information on configuring access for Oracle RAC database, see “Configuring Client Access for Oracle Database 10gR2 RAC” (page 381).
Configuring Oracle RAC Database in a Site Aware Disaster Tolerant Architecture
This section describes how to configure Oracle RAC database in a SADTA. The subsequent sections elaborate on the configuration procedures using Oracle Database 10gR2 RAC as an example.
Configuring Oracle RAC Database in a Site Aware Disaster Tolerant Architecture 361