Oracle Database Tips by Donald Burleson

Oracle10g Grid Computing with RAC
Chapter 8 - RAC Administration

Client Side Initialization Parameter File vs. Server Parameter File

By default, Oracle uses parameter settings in the server parameter file to control database resources. The traditional client side parameter file (init.ora) can also be used; however, Oracle recommends that you use the server parameter file because it is easier to use and manage.

The server parameter file (also called SPFILE) is in a single location where all the necessary parameters are defined and stored. The defined parameter values are applicable for all the instances in the cluster. The SPFILE permits dynamic changes without requiring you to bring down the instance.

You can still use the client side parameter file to manage parameter settings in Real Application Clusters; however, administrative convenience is sacrificed and the advantage of dynamic change is lost. By default, if you do not specify PFILE in your STARTUP command, Oracle will use a server parameter file.

Server Parameter File

A server parameter file is basically a repository for initialization parameters.  Initialization parameters stored in a SPFILE are persistent, meaning any parameter changes made while an instance is running can persist across instance shutdown and startup. In this way, all the initialization parameters manually updated by ALTER SYSTEM SET commands become persistent. It also provides a basis for the Oracle database server to self-tune.  Another advantage, particularly for multi-instance RAC systems, is that a single copy of the parameter file can be used by all instances. Even though a single file is used to specify parameters, it has different format styles to support both the common values for all instances, as well as the specific values for an individual instance.