limiting the size of the data kept

Thanks Don. Perfect. One more question. I suspect that when I run this CRON in the middle of the night I will also optimize these tables and also backup the entire mySQL database. This is the main reason I am trying to limit the amount of data I hold in my own mySQL. I figure I probably want to shut down my system while I am doing this, and then bring it back up when I am done with the CRON.

Is there anyway I could "signal" my CI apps to kick everyone off, and not allow any logins while this is going on? I think that PHP is running separate processes for each user. Is there any "shared memory" that each process could check before deciding to loggoff everyone?

Put another way, IS there a global variable (ie semaphore) that all the CI/PHP applications can see? I don't need the apps to wait on that semaphore since this is a multi process app.

proof that an old dog can learn new tricks