How can I change the amount of memory that the Store can use in Microsoft Exchange 2000 Server and later?

A. The Exchange Store is responsible for interfacing with the Exchange database files. Because these files are disk based, the Exchange server caches as much information as possible and the Store uses as much of the machine's memory as possible, up to a default maximum of approximately 858MB of RAM. The Store releases this memory when other processes need to use it. For instance, on a system with 1GB of RAM, you shouldn't be surprised if the Store typically uses more than 700MB. Having hundreds of megabytes of free memory serves no purpose, so the Store simply puts available memory to good use.

You can change the amount of memory that Exchange uses for its cache by carrying out the following steps (although you should fully test any such change because it might effect system performance):

  1. Install the Windows 2000 or later support tools from the server OS installation CD-ROM.
  2. Start the ADSI Edit utility, which is one of the support tools--go to Start, Run, and type
  3. From the left-hand pane, expand the root and expand the Configuration item.
  4. Expand Services (each item will be prefixed by CN=), Microsoft Exchange, <name of your Exchange Organization>, Administrative Groups, <name of the administrative group>, Servers, <Name of the server for which you want to modify the Store memory information>.
  5. Select the server. In the right-hand pane, you'll see a list of components that you can change.
  6. Right-click CN=InformationStore, then select Properties from the context menu.
  7. Select the Attribute Editor and ensure that the "Show optional attributes" option is selected.
  8. Double-click "msExchESEParamCacheSizeMax," as this figure shows.
  9. Although the value appears blank, Exchange sets this value to default to 219726. The value refers to the number of 4KB sections, otherwise known as pages. The system uses 4KB increments because the Extensible Storage Engine (ESE) database that Exchange uses stores data in 4KB sections. Enter a new value equal to the number of 4KB sections required. For example, to limit the Store to use 50MB of RAM, you'd enter a value of 12500 (you would never set the value this low on a production server--I'm just using it here as an example). Because of virtual address space limitations, Microsoft recommends that you enter a maximum value no larger than 307200, which is approximately 1.2GB of memory. You should typically increase the default value of 219726 only if you have more than 2GB of memory. For maximum efficiency, ensure that the value you enter is a multiple of 8192 (i.e., 2 pages). Click OK.
  10. Click OK to close the InformationStore Properties dialog box, then close the ADSI Edit console window.
  11. Before the change can take effect, the value for the setting you entered in Step 9 needs to replicate across the forest. After the change has replicated, you need to restart the Store on the targeted Exchange server for the change to take effect.
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