You can define user protocols for your application by specifying user data on a resource request. User data is 64 bytes of data that can be specified on any IXLLOCK request. Within the contention and notify exits, contents of the 64-byte user data field for each request on the resource request queue can be examined or modified — whatever the application requires to maintain its own controls about the serialization of the resource. An example of your use of user data is if your locking protocol supports lock states other than shared and exclusive. You can put your lock state information in the user data.