The XES lock services allow sysplex-wide serialization in a multi-system data sharing environment. The services provided through the IXLLOCK macro enable authorized applications to obtain shared or exclusive serialization on user-defined logical resources. Additionally, you can implement your own locking protocols through the inclusion of user data. The XES lock services offer the additional benefits of allowing you to assist in the management of contention in the data sharing environment and of providing failure recovery options by retaining data about serialized resources that will persist across system outages.

When you request an XES lock service, you must be connected to a lock structure in a coupling facility. The lock structure is the repository for the lock table used to monitor the serialization of resources in the sysplex and for the data being recorded for recovery purposes.

Intrinsic to the XES lock services are the user exit routines that provide the negotiation and contention management protocols for the data sharing application. The contention exit and the notify exit collaborate to resolve contention for shared resources. Other exits used by the XES lock services are the complete exit, to report the completion of a previously submitted request for a resource and the event exit, to report the occurrence of an event in the sysplex, such as another user failing, which might affect your processing.