What is SMS Agent Host service (CcmExec)? I have failed to find this information (e.g. there is no Wikipedia entry) - besides for information in some error cases on how to restart this service for dependent software. (The best I could find was: "ccmexec.exe is a part of the Microsoft SMS operating system service. This service calls upon another service, the SMS Agent Host. This program is important for the stable and secure running of your computer and should not be terminated." and SMS = Systems Management Server)
What purpose does it serve and why would it hold on to directory handles? E.g. may it scan the entire disk on behalf of some other service?
Is SMS Agent Host service specific to Windows Server 2003/Windows XP x64?
As you mentioned, this is the agent for Microsoft SMS. SMS can be used to collect inventory, apply patches, deploy software, etc. This is not something that is specific to Server 2003/Windows XP x64. This shouldn't be on a machine unless you have SMS deployed. You can stop the service if it's killing a machine, it just won't report back.
The newer versions of SMS are called System Center Configuration Manager.
Well said rorr,
Give this a look. It explains more about SMS/SCCM
http://en.wikipedia.org/wiki/System_Center_Configuration_Manager