Oracle DBA

Oracle Real Application Clusters (RAC) One Node is a high availability solution for Oracle Databases that runs on a single server. It is designed to provide the benefits of RAC, such as failover, scalability, and performance, without the need for multiple servers.

RAC One Node works by creating two instances of the database on the same server. These instances are known as the primary and standby instances. The primary instance is the active instance that handles all read and write requests. The standby instance is a passive instance that is synchronized with the primary instance. If the primary instance fails, the standby instance is automatically promoted to the primary role and begins handling requests.

RAC One Node is a good solution for organizations that need high availability for their databases but do not have the resources to deploy a multi-node RAC cluster. It is also a good solution for organizations that want to consolidate their database servers.

Here are some of the benefits of Oracle RAC One Node:

• High availability: RAC One Node eliminates the database server as a single point of failure. If the primary instance fails, the standby instance is automatically promoted to the primary role and begins handling requests.
• Scalability: RAC One Node can be scaled up to a full multi-instance RAC cluster by adding additional servers.
• Performance: RAC One Node can provide improved performance for some workloads by offloading tasks to the standby instance.
• Simplicity: RAC One Node is easy to deploy and manage. It requires no application changes and can be deployed on a single server.

To create an Oracle RAC One Node database, you can use the Database Configuration Assistant (DBCA). On the Deployment Type page, select Oracle RAC One Node database.

Oracle RAC One Node is a good solution for a variety of workloads, including:

• OLTP databases
• Data warehousing databases
• Mixed workloads

Oracle RAC One Node was first introduced in Oracle Database 11g Release 2. It was developed in response to customer demand for a high availability solution for Oracle Databases that could be deployed on a single server.

The development of Oracle RAC One Node was based on the following key technologies:

• Oracle Clusterware: Oracle Clusterware is a set of software components that provides the basic building blocks for clustering Oracle Databases.
• Oracle Automatic Storage Management (ASM): ASM is a disk management technology that simplifies the management of storage for Oracle Databases.
• Oracle Real Application Clusters (RAC): RAC is a high availability solution for Oracle Databases that allows multiple instances of a database to run on multiple servers.

Oracle RAC One Node uses the same architecture as RAC, but it only runs on a single server. This is achieved by using two instances of the database on the same server: a primary instance and a standby instance. The primary instance is the active instance that handles all read and write requests. The standby instance is a passive instance that is synchronized with the primary instance. If the primary instance fails, the standby instance is automatically promoted to the primary role and begins handling requests.

Oracle RAC One Node was initially designed for small to medium-sized businesses. However, it can also be used for larger businesses that need high availability for their databases but do not have the resources to deploy a multi-node RAC cluster.

Over the years, Oracle RAC One Node has been enhanced with new features and functionality. For example, in Oracle Database 12c Release 1, Oracle RAC One Node was enhanced with support for online database relocation. This allows you to move the database from the primary instance to the standby instance without having to take the database down.

In Oracle Database 18c, Oracle RAC One Node was enhanced with support for active-standby mode. This mode allows you to run read-only queries on the standby instance, which can improve performance for some workloads.