ZENworks zone with Antimalware enabled or the new Patch Feed enabled, OCM is mandatory and this will be automatically configured as part of the feature enablement.
The Ondemand Content Master requires an Internet connection to communicate and download content from the external Antimalware cloud service or Patch New feed external source such as Google or Microsoft etc. This service is a Content Distribution Network (CDN) that manages all the malware signature files required to disinfect files on managed devices for Antimalware and for the Patch New feed it will download the patches from external sources like Google or Microsoft and content will be download based on the requests from manage devices.
In a zone, it is always recommended to have a single OCM server as a minimum requirement, and the Administrator can decide to have multiple OCM servers depending on the scale requirements so that the overall load can be distributed among OCM servers in the zone.