Oracle Configuration File

Oracle configuration file:

Oracle reads configuration parameters from either server parameter file (SPFILE) or text initialization parameter file (PFILE). When you start database instance, it tries to read SPFILE in default location. Else it searches for pfile. The search order is as under:

• spfileORAACLE_SID.ora
• spfile.ora
• initORACLE_SID.ora

The default location for spfile and pfile is OH/dbs. If ASM is present, SPFILE default location is the same disk group as the datafiles.Alter system has optional scope clause that specifies the scope of the change

• scope=spfile : The change is applied only to spfile only which impliesNo change is made to the current instance. For both dynamic and static parameters, the change is effective at the next startup and is persistent.
• SCOPE=memory The change is applied in memory only which impliesThe change is made to the current instance and is effective immediately. For dynamic parameters, the effect is immedidate , but is not persistent as the server parameter file is not updated. This specification is not allowed for static parameters
• SCOPE=both  The change is applied to both server parameter file and memory which implies The change is made to the current instance and is effective immediately. For dynamic parameters, the effect is persistent. For static parameters, this specification is not allowed.

The default is both if SPFILE is used for startup and MEMORY if pfile is used for startup.
You can use deferred keyword for dynamic parameters, indicating to defer the change for the future sessions.