Overview of Oracle Real Application Clusters One Node

Oracle Real Application Clusters One Node (Oracle RAC One Node) is an option to Oracle AI Database Enterprise Edition.

Oracle RAC One Node is a single instance of an Oracle RAC-enabled database running on one node in the cluster, only, under normal operations. This option adds to the flexibility that Oracle offers for database consolidation while reducing management overhead by providing a standard deployment for Oracle AI Databases in the enterprise. Oracle RAC One Node database requires Oracle Grid Infrastructure and, therefore, requires the same hardware setup as an Oracle RAC database.

Oracle supports Oracle RAC One Node on all platforms on which Oracle RAC is certified. Similar to Oracle RAC, Oracle RAC One Node is certified on Oracle Virtual Machine (Oracle VM). Using Oracle RAC or Oracle RAC One Node with Oracle VM increases the benefits of Oracle VM with the high availability and scalability of Oracle RAC.

With Oracle RAC One Node, there is no limit to server scalability and, if applications grow to require more resources than a single node can supply, then you can upgrade your applications online to Oracle RAC. If the node that is running Oracle RAC One Node becomes overloaded, then you can relocate the instance to another node in the cluster. With Oracle RAC One Node you can use the Online Database Relocation feature to relocate the database instance with no downtime for application users. Alternatively, you can limit the CPU consumption of individual database instances per server within the cluster using Resource Manager Instance Caging and dynamically change this limit, if necessary, depending on the demand scenario.

Using the Single Client Access Name (SCAN) to connect to the database, clients can locate the service independently of the node on which it is running. Relocating an Oracle RAC One Node instance is therefore mostly transparent to the client, depending on the client connection. Oracle recommends to use either Application Continuity and Oracle Fast Application Notification or Transparent Application Failover to minimize the impact of a relocation on the client.

Oracle RAC One Node databases are administered slightly differently from Oracle RAC or non-cluster databases. For Oracle RAC One Node databases, you must monitor the candidate node list and make sure a server is always available for failover, if possible.

Note:

Oracle RAC One Node supports Transaction Guard and Application Continuity for failing clients over.
To prepare for all failure possibilities, you must add at least one Dynamic Database Service (Oracle Clusterware-managed database service) to an Oracle RAC One Node database.