ORA-12519, TNS:no appropriate service handler found

Error
Error connecting to database: (using class oracle.jdbc.driver.OracleDriver)
Listener refused the connection with the following error:
ORA-12519, TNS:no appropriate service handler found

Error occured while trying to connect to the database


Reason
Listener is up and running
The listener could not find any available service handlers that are appropriate for the client connection. (from oracle)

Solution
Execute below commands using sys user.
alter system set processes=300 scope=spfile;
shu immediate
startup