Back in the old days, many of the initialization parameters were not dynamically modifiable.If you wanted to use a different set of parameters for weekend batch processing compared to online use during the week, the DBA would have two parameter files -- two INIT. Now the DBA could not name them the same if they were in the same directory.
The location of the server parameter file is displayed on top of the page.
In the "old days," Oracle kept its parameters in a text file.
One can only use the above option with SPFILE's if the PFILE you point to (in the example above), contains a single 'SPFILE=' parameter pointing to the SPFILE that should be used.
Example: While a PFILE can be edited with any text editor, the SPFILE is a binary file.
This is the default behaviour if a PFILE was used at STARTUP.