Real Application Cluster (RAC) is a widely used Oracle cluster product that provides high availability and scalability for Oracle databases. When configuring Data Guard on RAC databases, there are some points that we need to take into consideration in order to build a proper integration. For a RAC primary database, we may prefer configuring single instance or RAC standby databases. These configurations will be discussed separately. A single instance primary database and RAC standby database configuration is not common and doesn't require any special attention.
Creating a single instance standby database for a RAC primary database is a very frequently encountered configuration. The following points are important when configuring a single instance standby for a RAC primary database:
LOG_ARCHIVE_DEST_n
parameter in the primary database, which shows the standby database, must be configured with the SID='*'
option. This will enable a redo transport service on all nodes of the primary database.LOG_ARCHIVE_DEST_n
parameter pointing to the standby database.(number of primary redo log groups + 1) * number of threads on primary
For example, if we have three redo log groups for each instance of a two-node RAC primary database, we must create (3+1)*2=8
standby redo log groups on the standby database. The size of the standby redo logs should be equal to that of the primary online redo logs. Use the following statement format to create standby logs:
ALTER DATABASE ADD STANDBY LOGFILE THREAD 1 GROUP 11 SIZE 100M, GROUP 12 SIZE 100M, GROUP 13 SIZE 100M, GROUP 14 SIZE 100M, ALTER DATABASE ADD STANDBY LOGFILE THREAD 2 GROUP 15 SIZE 100M, GROUP 16 SIZE 100M, GROUP 17 SIZE 100M, GROUP 18 SIZE 100M;
Now let's see what we should pay attention to when creating a RAC standby database for a RAC primary database:
LOG_ARCHIVE_DEST_n
parameters must be configured properly on every instance of the primary and standby databases to show remote archiving destinations. Remote destinations configured on the standby database will be used after a switchover.The integration of Data Guard and RAC was covered under the titles of two different configurations where the standby database is a single instance of a RAC. Using RAC with Data Guard is a common solution that combines high availability and disaster recovery purposes in a dependable way. Oracle recommends this configuration in its maximum availability architecture.