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. To determine where the transaction
is running WebSphere uses GRS. 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:
- Two-phase commit transactions involving more than one server
- HTTP sessions in memory
- Stateful EJBs
- "Sticky" transactions to keep track of pseudo-conversational states.
- If you are not in a sysplex, you should configure GRS=NONE.
- If you are in a sysplex, we strongly recommend GRS=STAR.
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.