Spfile/Pfile

Basic Info

 * SPFILE can be edited using alter system only, in memory or spfile or both.
 * PFILE can only be edited using editor.

Order of Search

 * Spfile$oraclesid.ora
 * spfile.ora
 * init$oraclesid.ora

Side Notes

 * If in V$SPPARAMTER, ISSPECIFIED is TRUE then spfile was used to startup else pfile.
 * In the EM, you have current tabs for memory parameters and spfile for shutdown persistent parameters.