XADM: Memory Usage of Store.exe Is Higher in Exchange 5.5

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In versions earlier than Microsoft Exchange Server 5.5, memory over 256 MB was not used. With version 5.5, memory up to 3 GB can be used and is used, as is evident in the Task Manager Processes.

Exchange Server 5.5 uses all available RAM for the best performance possible, unless memory usage is limited by using the Exchange Performance Optimizer. Exchange Server will release memory to other applications as required to increase system performance.

As per the Exchange Server 5.5 Readme.doc:

   Significant changes were made to the database engine allowing Microsoft
   Exchange Server to better use large memory and multiple processor
   servers. In particular, Performance Optimizer will set the maximum
   number of information store and directory database buffers to much
   higher values than before (approximately the amount of available RAM
   divided by 4K).