The parameter lists have no provision for an exit to pass information, such as the address of a work area, to another exit invocation. Your exit can pass information to another of your exits by calling IEANTCR to create a name/token pair. In another exit call IEANTRT to retrieve the information and IEANTDL to delete the information. See z/OS V2R2 MVS Authorized Assembler Services Reference EDT-IXG, SA23-1373.
You choose a 16-byte name for your 16 bytes of information. For example, you might choose a 12-byte constant and the 4-byte UCB address for the name. It is better not to choose a task level name because any of the exits can be called in various tasks. To avoid the possibility of permanently lost storage, use a home address space name.
Remember that the UCB address in TEPMUCB might be duplicated in another address space and represent a different UCB and device in the other address space.
Remember also that the device might be closed, varied offline and become undefined. In that case, a system-level name/token pair would be lost until IPL unless a device is defined and happens to get a UCB at the same virtual address. It is recommended that you delete your name/token pair in the last exit that uses it.