Understand the server pool concepts in Oracle Real Application Clusters (Oracle RAC) environments.
Policy-Managed Clusters and Capacity Management
Starting with Oracle Clusterware 11g release 2, resources that Oracle Clusterware manages are contained in logical groups of servers called server pools.
About Creating Server Pools for Oracle RAC Databases
You can create a server pool with Oracle Database Configuration Assistant while creating an Oracle RAC database, but Oracle recommends that you create server pools before you deploy database software and databases.