Assigning Resource Contention Management

XES chooses the contention exit of a connected user to manage resource contention in one of the following cases:

When a resource request queue becomes incompatible
When a new request for a resource is received that is incompatible with the existing entries on the resource request queue, the queue is said to be “in contention”. In this case, XES selects one of the connected users to manage the contention and presents the current resource request queue (containing the new, pending request) to the contention exit of the selected user.
When a previously selected resource contention manager fails.
If a connected user disconnects or abnormally terminates while it is managing one or more resource request queues through its contention exit, XES, as part of its cleanup processing, reassigns management responsibilities to one of the surviving connectors.

The following diagram depicts XES processing when it receives a new request for a resource.

Figure 1. Receiving a Resource Request

The selected connector will continue to manage the resource through its contention exit until XES is able to determine that all entries on the resource request queue are once again compatible. When this determination is made, contention management ends and XES grants any pending requests remaining on the resource request queue. The selected connector is no longer responsible for managing the resource. Should contention for the resource reappear, a different user might be selected to manage the resource.