questions about spfile
To change the parameters using spfile
1) does it require the DB to be down first?
2) If DB is NOT down while the parameter is changed, DB needs to be re-started?
3) I am NOT used to the spfile, can I do in the old fashioned way?
you can find the answers to your questions on SAP Note 601157.
1) you do not need to shutdown the database first,
2) Db needs to be restarted if you change static parameters.
3) As mentioned on note 601157, th are cases where "the init.ora file may exist several times on several hosts, which complicates the synchronization if a parameter is changed. This problem no longer occurs with a server parameter file."
So, you can still do it the old fashioned way. But, it is generally recommended to use the spfile.
Please, read the SAP note. You will find much more info there.