X starts new session when user logs off

Greetings,

We have a need for X to re-use X Server 0 each time a user logs off and logs back in. We noticed in RHEL 7, usually this number is incremented for the subsequent login.

Is this because the last sessions has not fully released all its resources before gdm starts a new session? If so, is there a mechanism to add a sleep command when X exits upon desktop logout that would allow 0 to be re-used consistently?

Otherwise, I need to understand how to set or control the DISPLAY environment variable such that when DISPLAY = :x.y, that x can be derived from the current session while y is specified by our scripts/software. Is this possible?

Thanks,
Greg