I'm doing some reading up on the advantages/disadvantages of using timestamps for concurrency control in a distributed database. The material I'm reading mentions that although timestamps overcome traditional deadlock problems which can affect locking there is still the problem of "global deadlock" which it is vulnerable to.
The material describes global deadlock as a situation where no cycle exists in the wait-for graphs of local graphs but that there is a cycle in the global graph.
I'm wondering how this could happen? Could someone describe a situation where a timestamp system could cause this problem?