Error: ORA-00018 maximum number of sessions exceeded
Cause: All session state objects are in use.
Action: Increase the value of the SESSIONS initialization parameter.
Solution: You have to increase processes and depends on this parameter which is sessions, transactions parameters.
Calculating amount of sessions and transactions parameter values with below formula.
processes=x
sessions=x*1.1+5
transactions=sessions*1.1
You can show and increase processes parameter like below.
SQL> show parameter processes;
processes integer 150
SQL> alter system set processes=300 scope=spfile;
SQL> shutdown immediate;
SQL> startup;
You should set the processes parameter to a very high value because it consumers very little resources and you do not want your instance to “lock up” with the ORA-0018 error.