using 'issys_modifiable' from "v$parameter" view
if it results
Immediate - we can change dynamically using spfile
False - Need to bounce the database to get it reflect from pfile
EX:- select name,issys_modifiable from v$parameter where name='UNDO_RETENTION';
NAME issys_modifiable
-------------- ------------------------
undo_retention Immediate
Now change it with
alter system set undo_retention=1800 scope=both;