About Creating Server Pools for Oracle RAC Databases

You can create a server pool with DBCA while creating an Oracle RAC database, but Oracle recommends that you create server pools before you deploy database software and databases.

Oracle also recommends that you:

Enable role separation before you create the first server pool in the cluster.
Create and manage server pools using configuration policies and a respective policy set.

You can implement role-separated management in one of two ways:

Vertical implementation (between layers) describes a role separation approach based on different operating system users and groups used for various layers in the technology stack. Permissions on server pools and resources are granted to different users (and groups) for each layer in the stack using access control lists. Oracle Automatic Storage Management (ASM) offers setting up role separation as part of the Oracle Grid Infrastructure installation based on a granular assignment of operating system groups for specific roles.
Horizontal implementation (within one layer) describes a role separation approach that restricts resource access within one layer using access permissions for resources that are granted using access control lists assigned to server pools and policy-managed databases or applications.

For example, consider an operating system user called grid, with primary operating system group oinstall, that installs Oracle Grid Infrastructure and creates two database server pools. The operating system users ouser1 and ouser2 must be able to operate within a server pool, but should not be able to modify those server pools and withdraw hardware resources from other server pools either accidentally or intentionally.