create pfile from spfile without a running instance

when you messed up an instance and need to change some parameters in your PFILE, but what you have is only an SPFILE, which is not editable, you can still get yourself a pfile in case if you're running on unix. There's a

strings

command, which will extract printable strings from spfile.

$ strings spfile$ORACLE_SID.ora > pfile$ORACLE_SID.ora

Unsetting the instance parameters

Following syntax is used to unset a parameter:

SQL> alter system reset [parameter_name] scope=spfile sid='*';

where "sid" is the sid of the instance which needs to be affected in a RAC environment. In case of a single instance use "*".