Oracle Single Instance Vs RAC Vs RAC One Node
There are three types of deployment options you have :
1.Oracle Single Instance (Single Instance)
2.Oracle Real Application Cluster (RAC)
3.Oracle RAC One Node
Below are the overview of these databases :
Single Instance:
Single Instance is a simple and basic option of deploying oracle database. In single instance database there is only one instance of database running on one node. Single Instance is simple to install and maintain. This could be a good choice for small production and development environments.
Oracle RAC Database:
Oracle RAC database is a clustered database. It can have more than one instance running on one or more hosts. To make is database RAC , there is another software needs to be installed called Oracle Grid infrastructure which takes care of multinode sync, ASM, Oracle restart etc. Oracle GI is necessary as a base of Oracle RAC. In Oracle RAC, the load is balanced across multiple instance of databases running on different nodes. This is best for Production database. Failure of any instance is abstracted from user and forwarded to another instance from the database server pool. No of instances can be controlled using Policy Managed or Admin Managed.
Oracle RAC One Node:
Some time we need to have RAC databases but don't need many instances, why? Simple answers to it is leverage the high availability of RAC. The Oracle RAC One node is a RAC DB runs on one host. The advantage is it saves your resource, can to converted to full RAC any time, Cluster fail over i.e. the Database instance is moved to new instance in case of any failure on host known as Instance Relocation, easy to upgrade etc. This type of database is well suited for small production and dev/test environments.
