ORA-00020: maximum number of processes 150 exceeded

PROCESSES specifies the maximum number of operating system user processes that can simultaneously connect to Oracle

SQL> show parameter processes

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

processes                            integer     150

SQL> alter system set processes=250 scope=spfile;

System altered.

(the new value takes effect the next time you start an instance of the database.)

if you issue:

SQL> alter system set processes=250 scope=both;

alter system set processes=250 scope=both

                 *

ERROR at line 1:

ORA-02095: specified initialization parameter cannot be modified

after you restart database query for the changes

SQL> select * from gv$resource_limit;

or

SQL>show parameter processes