Sudden spike on DB processes

Hi guys, would want to know what sort of investigation can be done from DB layer if the DB suddenly max out on the number of processes it's been allocated?

Had an urgent call from my company on 1 fine weekend saying that their application failed to connect to the DB. Based on the error code (ORA-00020) i know that the process limit has max out.

So the only workaround I can think of is to forcefully kill of some of the Oracle processes from OS layer to allow me to connect to the DB.

Once in, I run through the connected sessions and found that a particular application server is spawning thousands of sessions to the DB. Then I proceed to kill all the sessions from that particular machine and inform the apps guys to check on their application server. However a few hours later, they called and same thing happen, apps can't connect to DB with the same ORA-00020 error. I did the same workaround but this time, I request the apps guys to shutdown that particular apps server and ask them to check. Issue no longer happen again.