ORA-00018

ORA-00018 : maximum number of sessions exceeded Cause : All session state objects are in use Action : Increase the value of the SESSIONS initialization parameter

To increase the value of the sessions:

1. login to you oracle as sysdba:
sqlplus "/ as sysdba"
2. use the following command to alter your session at the sqlplus prompt
sql>alter system set sessions = (number of session i.e.200) scope = spfile ;
3. restart your database to take effect.
at the sqlplus prompt enter
sql> shutdown immediate;
sql> startup;