Method and apparatus for optimizing the handling of synchronous requests to a coupling facility in a sysplex configuration

摘要

A method and apparatus for optimizing the handling of a synchronous request issued from a system partition of a logically partitioned machine to a selected coupling facility. The coupling facility may be either an internal coupling facility residing in a separate logical partition or an external coupling facility residing on a separate physical machine; an internal coupling facility in turn runs on processors that are either dedicated to the coupling facility or shared with another logical partition. A logical partition manager maintains state information for each system partition indicating whether the partition is connected to an internal coupling facility. To ascertain the shared or non-shared status of a particular coupling facility to which it is connected, a system partition issues a Read Facility Parameters (RFP) command to the target facility, which responds with a message response block (MRB) containing a bit that is 1 if it uses dedicated processors and 0 if it uses shared processors. The system partition stores this information in an entry for the coupling facility kept in a shared/dedicated attribute table maintained by the partition. Each time the system partition issues a subsequent request to a coupling facility, it sets a bit in a message operation block (MOB) of the request to indicate the shared status of the facility, as indicated by the corresponding entry in its shared/dedicated attribute table. The processor executing the request examines the MOB bit as well as the state information maintained by the logical partition manager for the partition. A synchronous request to a coupling facility is converted to an asynchronous request if (1) the state information maintained by the logical partition manager indicates that the originating system partition is connected to an internal coupling facility and (2) the MOB bit indicates that the target coupling facility uses shared processors. Otherwise, a synchronous request is issued to the target facility without being converted to an asynchronous request.