Parameters

At the point of entry, CA VM:Tape passes the following parameter list to this exit using Register 1:

R1 =>	+0	A(VM user ID)
	+4	A(VM account code)
	+8	A(Command)
	+12	A(Access type)
	+16	A(TMC record for requested volser)
	+20	A(Message buffer)
	+24	A(Common User Exit Buffer)

A user can change two of these fields: A(Message buffer) and A(Common User Exit Buffer).