Recently, I was approached for clarification on CMCAPACITY table and what does it do. Well here's the simple answer
The CMCAPACITY table keeps track of the registered dispatchers. Just do a test on your machine, when you start CM, you'll see your dispatcher with usage = 4 and when you shutdown, it should be blank.
If CM has a row = 4 and CM is not running, it could have been improperly shutdown or something of that nature. If there is a usage of 4, it can prevent CM from locking the content store DB on start-up of IBM Cognos.
Well, if you love complex answers, there an developer works article and utilities about understanding your Cognos Content Store database using Content Manager Size and Browser Tools
You can get that here http://www.ibm.com/developerworks/data/library/techarticle/dm-0808masters/