WebSphere for z/OS uses GRS to communicate information between servers in a sysplex. When there are multiple servers defined in a system or a sysplex, a request may end up on the wrong server. WebSphere uses GRS to determine where the transaction is running. Therefore, if you are using global transactions, WebSphere will issue an enqueue for that transaction at the start of the transaction and hold on to that enqueue until the transaction ends. WebSphere for z/OS uses GRS enqueues for the following:
This requires configuring GRS to use the coupling facility. All of the WebSphere enqueues are issued with RNL=NO, which prevents misconfiguring the GRSRNLxx with inappropriate values. See the GRS documentation for details on setting this up.