CF Server performance issue

I'm a bit mystified that folks would offer that little bit of info and ask, "please advise". You say you're "not sure what's causing it to go down". Well that's job 1. You can't go on what people guess at. What do the logs say? And not just the [CF]/logs, but the [cf]/runtime/logs (or the [jrun]/logs, if on the Multiserver form of deployment). And do you see any *pid*.log files in the [cf]/runtime/bin (or [jrun]/bin) directory?

I realize these may be new resources for you to consider, so sorry if I'm sounding a bit harsh. I'm just saying these are where you need to start looking. I'm sure someone might reply to your questions about Access, and certainly one could argue that you should never use it, but before concluding that they necessarily have anything at all to do with the problem, look instead for the facts provided by the log files. CF doesn't just go down for no reason.

Or is the problem not that it goes down, but that it becomes unresponsive? You say you're on CF8. Is that Enterprise or Standard? If the former, what do you see going on in the Server Monitor? If you're on Standard, consider tools like FusionReactor or SeeFusion (commercial tools with trial editions) to help give you still more diagnostics to go on, or look into the JRun metrics feature.

I realize that it's easy to feel at a loss, and that CF is a black box. It's really not. You just need to know where to look and how to connect the diagnostic dots. There's a good series of recent troubleshooting blog entries by Mark Kruger, starting at http://www.coldfusionmuse.com/index.cfm/2008/8/11/troubleshooting-part1-gathering-information. There are similarly compelling troubleshooting blogs from Steven Erat, Brandon Purcell, Robi Sen, and others. I'm not discouraging your asking here. I'm just trying to help give you more resources to consider.

Hope that's helpful.