5.

Each server periodically sends its local WFG to a global WFG coordinator, which
combines all the local WFGs into a gloabl WFG. The global WFG coordinator then
searches cycles in the global WFG. 

A phantom deadlock is a cycle in the global WFG, which actually is not a 
deadlock in the present state. The problem arises because the local WFGs 
are sent to the coordinator periodically. 

Assume for example two processes P1 and P2. P1 executes on site S1 and 
P2 on site S2. P1 waits for some resource locked by P2 and P2 waits for some
resource locked by P1. 

Local WFGs:
	S1: P1 -> P2
	S2: P2 -> P1
	
The local WFGs are propageted to the global WFG coordinator. The coordinator
creates the global WFG and detects a cycle implying a deadlock. 

The same time process P1 might have been aborted releasing its resources. 
The coordinator might decide to kill P2 to brake the cycle, altough there was 
no deadlock in the present state of the system, the coordinator just thought 
there was.