I have Linux machine dedicated to serving static contents and PHP pages with Apache. Apache also work as a reverse proxy in a subdomain. I moved the PostgreSQL database to another Linux machine.
Is it safe to disable the OOM killer in the kernel?
If the OOM killer is running then it is likely that the OOM killer needs to be run to avoid the machine simple grinding to a halt as nothing, even the kernel, can allocate new memory if needed. The OOM killer exists because it is generally better to have some services fall over due to the killer than the whole machine to fall off the face of the 'net.
If you see the OOM killer in action with any regularity then you should either reconfigure the services on the machine to use less RAM, or you may need to add more RAM to the machine.