Oracle ORA-03135 connection issue with PowerSchool

Our PowerSchool Production instance is locally hosted and is protected by a firewall. Our school website runs on WordPress (is hosted on AWS) and authenticates users of different types (Parents, Students, Teachers and Staff) directly using a custom plugin I designed.

The issue reported was that some Parents were not able to log in. The issue was not consistent across all parents but just some of them, that too with specific usernames.

A closer look at the SQL being executed for authenticating the users revealed an Oracle connection error:

ORA-03135: connection lost contact Process ID: 12888 Session ID: 192 Serial number: 44200

A quick Google search revealed the possible causes as below:
http://www.vitalsofttech.com/ora-03135-connection-lost-contact/
http://www.dba-oracle.com/t_ora_03135_connection_lost_contact.htm

When PowerSchool engineers investigated this, they pointed out that the SQLNET.EXPIRE_TIME variables are not set on our instance and they advised against changing those variables.

A further investigation of this issue at our end revealed an observation that when our PowerSchool instance and school website were on same network, that is, either locally hosted or on Amazon Web Services, the issue doesn’t occurs. Only as long either of the server is on different network that we face this issue. Firewall seems to be the culprit, however, our network administrator confirmed the connections were not being blocked by firewall at all.

We chose to restart the PowerSchool Services. It did not immediately resolve the problem, however, the problem did go away eventually on its own the next day or so. It appears that this might have been a combination of the restart of PowerSchool services and some nightly executed processes in PowerSchool (and of course some magic).

We hope that if you encounter such issue, restarting of services in your server would help.