Show Parameter Spfile
Whenever you want to know the location of Server Parameter File (SPFILE), I think the first thing you want to do is to show the parameter value of SPFILE in SQL*Plus.
SQL> show parameter spfile;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
spfile string /u01/app/oracle/product/12.1.0
/dbhome_1/dbs/spfileORCL.ora
Null or Empty Value
When you found there's nothing or blank value by SHOW PARAMETER SPFILE like this:
SQL> show parameter spfile;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
spfile string
That's because the database started up with a Parameter File (PFILE), not the Server Parameter File (SPFILE), even worse, the instance can't tell where the PFILE that started up the database is.