XADM: Computer That Is Running Exchange 2000 and Windows 2000 Server May Run Out of Virtual Memory with Event ID 12800 (302254)

Event Type:  Error
Event Source:  MSExchangeIS
Event Category: Content Engine 
Event ID:   12800
Description:
Message processing failed because there is not enough available memory 
(8007000E-82000387).
					

MORE INFORMATION

In Exchange 2000 Server Service Pack 1 (SP1), memory is allocated more reasonably, and the JET database cache shrinks more aggressively to give up some memory when the information store is approaching the virtual address space limit. In Exchange 2000 Server SP1, the amount of virtual address space that is allocated each time that a storage group is mounted is decreased. In Exchange 2000 Server SP1, changes were made to some of the default values that are used to calculate the amount of space that is allocated, so on a two-processor computer, only 12 MB is allocated for each storage group, and on an eight-processor computer, only about 27 MB is allocated. JET does not make any specific allocations based on the number of Messaging Databases (MDBs), or stores, in the storage group, only allocations based on the number of storage groups. However, the store does make some memory allocation for each MDB, but it is a fairly insignificant amount.

The amount of memory for each thread that the store allocates also changes. In Exchange 2000, the store allocated 1 MB for each thread. In Exchange 2000 Server SP1, this is cut in half to 500 kilobyte (KB) for each thread. The store can often run with 300 or more threads, so this change can save a significant amount of memory.

Finally, the algorithm for JET to cut back its database cache size when the virtual memory is approaching the limit is changed. In Exchange 2000, JET backs off only when the available address space is less than 64 MB. In Exchange 2000 Server SP1, JET backs off when the available address space is less than 10 percent of the total. For a computer with 2 GB of virtual address space (for example, a Windows 2000 Server-based computer), JET backs off when the virtual address space is less than 200 MB. On a computer with the /3GB switch, JET backs off when the virtual address space is less than 300 MB. JET's aggressiveness in backing off in Exchange 2000 Server SP1 reduces the chance that the problems that are seen in Exchange 2000 will occur. When the total amount of virtual address space that is available is over 200 MB, it is less likely that much of that space will be so fragmented that it is unusable.

However, when the JET database cache is smaller, performance on the server is decreased. With a smaller JET database cache, disk input/output (I/O) on the MDB drive increase. Also, you might see a slight increase in CPU usage on the server. Finally, client latencies generally increase with a smaller JET database cache.

You should run Exchange 2000 on a Windows 2000 Advanced Server-based computer and set the /3GB switch in the Boot.ini file. You can run Exchange 2000 on a Windows 2000 Server-based computer, but after you approach the virtual address space limit, performance begins to decrease as the JET database cache size shrinks.

IMPORTANT: Note that it is not recommended that you run Windows 2000 Server with anything more than 2 GB of memory (that is, do not use the /3GB switch), when you are running Exchange 2000 because anything over that amount is unused. If the Store.exe process runs out of virtual address space, the memory is all on the server. To get the best use out of the added memory, run Windows 2000 Advanced Server, not Windows 2000 Server. The /3GB switch has advantages only when you use it on a Windows 2000 Advanced Server-based computer.