DB console cannot connect to the database due to ORA-12516 errors

Oracle 11gr2 on win 32 bit, after upgrading from oracle 11gr1 to 11gr2 ORACLE ENTERPRISE MANAGER was not getting started and failed with ORA-12516 error.

TNS-12516 TNS:listener could not find instance with matching protocol stack
TNS-12519 TNS:no appropriate service handler found

Cause: processes parameter was set on default value i.e.: 150

Solution: Increase processes parameter value to appropriate digit.

How to increase processes parameter value?

1. connect to database with SYSDBA user

2. execute the following sql statement

alter system set processes = [appropriate value] scope=spfile;

3. shutdown database

shutdown immediate;

4. startup database

startup

5. check processes parameter value

show parameter processes

Now try to restart ORACLE ENTERPRISE MANAGER SERVICES

cmd> set oracle_sid =[sid]

cmd> emctl start dbconsole