Starting with Oracle Clusterware 11g release 2, resources that Oracle Clusterware manages are contained in logical groups of servers called server pools.

Resources are hosted on a shared infrastructure and are contained within server pools. Resources are no longer defined as belonging to a specific instance or node. Instead, the priority of resource requirements is defined. You can use a cluster configuration policy set to provide dynamic management of cluster policies across the cluster.

• Server Pools and Server Categorization
  You can manage servers dynamically using server pools by identifying servers distinguished by particular attributes, a process called server categorization.
• Server Pools and Policy-Based Management
  With policy-based management, database administrators specify the server pool (excluding Generic or Free) in which the database resource runs.
• How Server Pools Work
  Server pools divide the cluster into groups of servers hosting singleton and uniform database services and applications.
• Default Server Pools
  When Oracle Clusterware is installed, two server pools are created automatically: Generic and Free.