@ianmud 

Not sure you mean "OC200 disconnect from network" or "Omada devices disconencted from the OC200 controller".

Controller can only manage the "Connected" devices. Upgrade Sechdule won't take effect if the controller cannot communicate with the omada devices.

Note it has nothing to do with cloud account. The controller will try to find the update even you disable Cloud Access function. 

  @Somnus  By leaving the OC200 disconnected, I mean disconnected from Omada Cloud Access. The question is whether the Services ==> Upgrade option requires the OC200 to be connected to Omada Cloud Access at the time of the scheduled operation.  The devices themselves remain under management of the OC200 at all times.  Any guideance is appreciated.  Thanks

  @ianmud TPLink has moved to requireing Cloud Access to be turned-on for the controller to download and apply updates.  The update automation might run without Cloud Access On, but will likely perform no actions (i.e. silently fail).

I think the update schedule has no relation to the cloud. My OC200 is not connected to the cloud and I had the Update Schedule active lately, at night. One morning my switches where updated by the controller without me doing anything. As this update caused problems I have deactivated the schedule.

  @ianmud 

Like @modebm said, Update Schedule will take effect even you disable the Cloud Access.

However the controller require Internet to make it work. If the controller does not have a correct gateway/DNS server, it will not be able to require update from cloud.