Q: What are the current recommendations for memory optimizations in Exchange 2003?
A: The article 815372 “How to Optimize Memory Usage in Exchange Server 2003” mentions the current recommendations. There you will find information about the /3GB switch as well as the /USERVA switch. What you may not have been aware about is the recommended change in the registry having to do with the HeapDeCommitFreeBlockThreshold. The recommended value to use for HeapDeCommitFreeBlockThreshold is 0x00040000 (in hexadecimal format). For additional information, click the following article number to view the article in the Microsoft Knowledge Base: 315407 “XADM: The 'HeapDecommitFreeBlockThreshold' Registry Key“.
You may have noticed that the Registry key name is mentioned as either HeapDeCommitFreeBlockThreshold or HeapDecommitFreeBlockThreshold (case difference) in some articles. While some Registry key values are case sensitive, Registry key names are not, so either should work for you.
UPDATE: Changed a broken link to 315407.