Since Sp1 released on Tuesday, I've received a number of reports that folks are seeing store taking a lot more memory than it did prior to SP1. This is showing up in monitoring programs like MOM or the SBS Monitoring, from what I understand, so it's causing a bit of concern for people. I figured the change that caused this is worth a post.
For starters, it's OK. This is by design and it's important to know that the Store.Exe process ISN'T really taking up hundreds of extra MB of actual memory. Unless you're experiencing performance issues due to this (and you shouldn't be), you may wish to simply adjust the monitoring thresholds and move on.
Prior to Exchange 2003 SP1, the virtual memory dedicated to Jet database cache is all allocated as “mapped bytes”. The change made in Exchange 2003 SP1 is that this database cache is all allocated now as “private bytes”. This causes the memory size reported by Store.Exe to be dramatically larger in terms of “private bytes” (by default 900mb larger) than prior to applying SP1. But overall, the “working set“ and “virtual bytes“ counters should be nearly unchanged. No additional memory is really being taken -- it's just being reported differently.
What this will principally affect is any reporting or monitoring software which is keying off “private bytes”. These will now see a big chunk of additional memory in use, and will potentially exceed configured thresholds. The MOM Management pack for Exchange 2003 Server has been updated to coincide with the release of Exchange 2003 SP1, and it takes this change into account.