ORA-00020 maximum number of processes exceeded

ORA-00020 maximum number of processes exceeded

Cause: All process state objects are in use.

Action: Increase the value of the PROCESSES initialization parameter.

ORA-00020 comes under "Oracle Database Server Messages". These messages are generated by the Oracle database server when running any Oracle program.

Reference: Oracle Documentation

How to increase PROCESSES initialization parameter:
1.    Login sqlplus
       sys as sysdba

NOTE:- if you are not able to connect with sys as sysdba then you need to stop the listener and then try and after connecting then start the listener or manuly kill find the process and kill them then try ....       

2. Check Current Setting of Parameters

sql> show parameter sessions
sql> show parameter processes
sql> show parameter transactions

3.    If you are planning to increase "PROCESSES" parameter you should also plan to increase "sessions and "transactions" parameters     A basic formula for determining these parameter values is as follows:

  processes=x     
 sessions=x*1.1+5    
 transactions=sessions*1.1     

4.    These parameters can't be modified in memory. You have to modify the spfile only (scope=spfile) and bounce the instance.

sql> alter system set processes=500 scope=spfile;

sql> alter system set sessions=555 scope=spfile;

sql> alter system set transactions=610 scope=spfile;

 sql> shutdown abort 

sql> startup

All The best.....:)