Maximum number of process exceeded error ::   Requires downtime  of  Oracle DB 

ORA-00020: maximum number of processes (150) exceeded
 277993
Journeyer
277993 Apr 23, 2008 8:47 AM (in response to 611251)
The problem may be because you were changing init ora file while your database starts with spfile. 

SQL>alter system set processes = 500 scope=SPFILE;
SQL>shutdown immediate
SQL>startup
SQL> show parameter processes

SQL> select name, ISSYS_MODIFIABLE from v$parameter where name='processes';

NAME
--------------------------------------------------------------------------------
ISSYS_MOD
---------
processes
FALSE