IGWLSHR can be used by applications to determine the PDSE sharing protocol currently in use. When PDSE extended sharing protocol is in use, you can modify the OPEN macro and the access method to improve performance for your programs. If you are not updating the PDSE, you can open the PDSE and do reads and writes from all systems. If you are sharing PDSEs using normal protocol, ensure that only one user is on one system at a time.

IGWLSHR is invoked by issuing a program CALL accompanied by a parameter (IGWLSHR) identifying the DFP share attributes call service, a list of arguments, and a storage area to return the result. You can use the information obtained from IGWLSHR to optimize PDSE access protocols. With concurrent sharing of a PDSE for output between multiple MVS systems, you can open a PDSE for OUTPUT for an extended period without locking out other INPUT or OUTPUT sharers of the PDSE. The exception is opening for update-in-place, which obtains exclusive control of the PDSE for one MVS instance.

Related reading: See z/OS DFSMSdfp Advanced Services for information about the DFP share attributes callable service.