I'm getting ORA-03135 error while I'm trying to connect to a database
This is an Oracle problem.
You also can not connect to the same database with the same Oracle Home using SQL*PLus.
ORA-03135: connection lost contact
1) Server unexpectedly terminated or was forced to terminate.
2) Server timed out the connection.
1) Check if the server session was terminated.
2) Check if the timeout parameters are set properly in sqlnet.ora.