How does pfile sync up with spfile

Question

When the parameter changed through :
alter system ... scope=spfile
when does pfile sync up with sp file? what process make that happen, or does this has to be done manually?
Thanks

Answer 1

This has to be done manually via the following command:
create pfile from spfile;
- this will create a file named init[SID].ora in your $ORACLE_HOME/dbs directory, by default.
In this way, you can 'backup' your current spfile settings by using the command:
create pfile='?/dbs/initSID.2009-05-30.ora';
If you wanted to know how to startup the instance using your pfile settings, you'd need to using the startup PFILE command (otherwise it would automatically default to using the spfile). For example, to start the instance using the backup you just created:
startup pfile='?/dbs/initSID.2009-05-30.ora';