The more common VMS/Access Control Alarm Integration option would appear to be the one in which the Access Control system manages the event/alarm and is supported by the associated Camera(s) images popping up in the Access Control system.
Another option would be to have the Access Control system send the alarm event to the VMS system and some access control information is presented in the VMS (e.g. present relevant camera images, classify provide alarm location on map, present card holder details) and also the Operator could undertake some access control functions within the VMS system (e.g. Acknowledge/Close Alarm Events, classify alarm event as 'false' , open door, secure door). "Two way" integration if you will.
What are the considerations for determining which way you should go?
Here's a few that come to mind:
1. What is the Operator's 'home' system (where do they spend most of their time - VMS or Access control?)
2. What % of access control points are covered by CCTV cameras (don't want to introduce two processes for access control? Why deal with an access control alarm that is not supported by video? in a VMS system )
3. Cost. Two way integration would likely be more expensive than a Video Pop-up within the Access Control system.
4. How is the Operations Area set-up? Different operators for Access Control and CCTV?
5. What system is more important to the organisation (or more widely used?)
6. Are there existing Acces Control / VMS integration products available?
Who provides them the Access Control vendor or the VMS vendor? (it would appear that these are primarily provided by the Access Control vendor for integration with popular VMSes into their Access Control system, i.e. the video pop-up within the Access Control system user interface.)