Exchange Cache Test

This test measures the performance of the Exchange Server Directory Service Access (DSAccess) cache. The DSAccess cache is a shared memory cache that is used by several components such as the information store, message categorizer (a component in that handles distribution lists), message transfer agent (MTA, used in non-SMTP delivery) or any other component or service that requires directory service information. This cache improves the performance of messaging operations like sending e-mails and provides access to both configuration information and recipient data from the Active Directory to Exchange server. The idea of DSAccess cache is used to reduce the number of queries going directly to the Active Directory. This caching implementation helps to reduce the cost overhead associated with the direct access to the Active Directory.

To attain the maximum performance, the cache memory can be increased by tuning the registry key “MaxMemory” available under the tree

“HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeDSAccess”.

Target of the test : An Exchange server 2000/2003

Agent deploying the test : An internal agent

Outputs of the test : One set of results for every Exchange server being monitored.

Configurable parameters for the test

Parameters	Description
Test Period	How often should the test be executed.
Host	The IP address of the machine where the Exchange Server is installed.
Port	The port number through which the Exchange server communicates.
IsPassive	If the value chosen is Yes, then the Exchange server under consideration is a passive server in an Exchange cluster. No alerts will be generated if the server is not running. Measures will be reported as “Not applicable’ by the agent if the server is not up.

Measurements made by the test

Measurement	Description	Measurement Unit	Interpretation
Cache hit ratio	This measure indicates the rate at which the events are being generated in the DSAccess cache. (An event is generated whenever an object has been located in the DSAccess cache or whenever new objects have been added in the cache.)	Percent	A zero value for this measure may indicate that the Exchange server is not performing any activity on the Active directory or no operations are happening on the Exchange server itself. A non-zero value indicates that the directory service has found the required objects in the DSAccess cache thereby reducing the access to the Active Directory. A non-zero value for this measure also may indicate that the required objects are not found in the DSAccess cache thereby resulting in the addition of newer objects from the Active Directory. A high value for this measure ensures better performance of the Exchange server.