The OOM uses a heuristic to figure out what to kill. If the primary purpose of your system is to run some process that hangs on to a lot of RAM, that heuristic is exactly the opposite of what you need, so it would a good idea to disable it or exempt that process.

Also, while I'm talking prophylactics, if you have (which you should) monitoring and alerting in your production environment, it seems like there should be an alert for whenever the OOM killer activates. Assuming you are allocating resources carefully enough that you expect everything to fit, if it fires, it's almost always a sign that things are not going according to plan and need to be investigated sooner rather than later.