Register 1 points to a three-word area that contains addresses of the CPRB, the connectivity environment descriptor (CED), and a parameter list (parmlist) from the server initialization/termination program. Of the three:

• The CPRB contains the service request.
• The CED is for MVSSERV use only. (If the server issues the DEFSERV, SENDREQ, or CHSTRACE macros, it must pass the CED address.)
• The server parmlist can point to resources such as data sets for the server to use. (For details about creating the server parmlist, see Designing and Writing a Server Initialization/Termination Program.)