INSTANCE_GROUPS is a Real Application Clusters parameter that you can specify only in parallel mode. Used in conjunction with the PARALLEL_INSTANCE_GROUP parameter, it lets you restrict parallel query operations to a limited number of instances.

This parameter specifies one or more instance groups and assigns the current instance to those groups. If one of the specified groups is also specified in the PARALLEL_INSTANCE_GROUP parameter, then Oracle allocates query processes for a parallel operation from this instance.

PARALLEL_INSTANCE_GROUP is a Real Application Clusters parameter that you can specify in parallel mode only. Used in conjunction with the INSTANCE_GROUPS parameter, it lets you restrict parallel query operations to a limited number of instances.

This parameter identifies the parallel instance group Oracle will use for spawning parallel execution processes. Parallel operations will spawn parallel execution processes only on instances that specify a matching group in their INSTANCE_GROUPS parameter.

If the value assigned to PARALLEL_INSTANCE_GROUP is the name of a group that does not exist, then the operation runs serially. No parallelism is used.

PARALLEL_MAX_SERVERS specifies the maximum number of parallel execution processes and parallel recovery processes for an instance.

PARALLEL_MIN_SERVERS specifies the minimum number of parallel execution processes for the instance. This value is the number of parallel execution processes Oracle creates when the instance is started.

PARALLEL_SERVER (replaced by CLUSTER_DATABASE)

PARALLEL_SERVER_INSTANCES (replaced by CLUSTER_DATABASE_INSTANCES)