PARAMETER Files : To start an instance, Oracle must read a parameter file.A parameter file is a text file containing a LIST of instance configuration parameters. You SET these parameters to particular values and to initialize many of the memory and process settings of an Oracle instance. Among other things, the parameters of this file tell Oracle the following:

• the NAME of the database for which to start up an instance.
• how much memory to use for memory structures in the SGA.
• what to do with filled online redo log files.
• the names and LOCATIONS of the database’s control files.
• the names of private rollback segments in the database.

Parameter Files : To start an instance, Oracle must read a parameter file.A parameter file is a text file containing a list of instance configuration parameters. You set these parameters to particular values and to initialize many of the memory and process settings of an Oracle instance. Among other things, the parameters of this file tell Oracle the following: