In some situations, a server cannot specify certain LUs as the local LU on its call to the Register_For_Allocates service. Use Table 1 to determine whether your server can specify a particular local LU.

In Table 1, a "yes" or "no" indicates whether a server in the address space in the left column (Column 1) is permitted to specify a particular local LU. If an address space attempts to register for an LU it cannot use, APPC/MVS fails the request with return code 16 (atbcts_request_unsuccessful) and reason code 15 (atbcts_not_auth_to_local_lu).

Column 1 lists different types of address spaces that contain servers attempting to register. The top two entries in column 1 show address spaces that are not "owned by" (connected to) a transaction scheduler. Typical examples of such address spaces are TSO/E address spaces and JES batch initiators. The last four rows of Table 1 show address spaces that are owned by transaction schedulers.

Address spaces can also differ depending on whether their conversations can flow through the system base LU (the default LU). Normally, an address space's conversations can use the system base LU. If an address space is to be later connected to a transaction scheduler, however, the scheduler might need to limit the address space's conversations to LUs owned by the scheduler. Here, the scheduler would prohibit the address space from using the system base LU through the Set_AS_Attributes service.

For information about the system base LU, see z/OS MVS Planning: APPC/MVS Management. For information about writing transaction schedulers and using the Set_AS_Attributes service, see z/OS MVS System Messages, Vol 3 (ASB-BPX).

The columns to the right of Column 1 in Table 1 show the results when servers attempt to register for different types of local LUs. Column 2 shows the results when servers specify NOSCHED LUs when registering. (A NOSCHED LU is an LU that is not associated with a transaction scheduler. Like other LUs, NOSCHED LUs are defined through the LUADD statement in the APPCPMxx member of the parmlib concatenation. For more information about defining NOSCHED LUs, see z/OS MVS Initialization and Tuning Reference.)

Columns 3 and 4 of Table 1 show the results when servers attempt to register for LUs that are owned by different transaction schedulers ("scheduler A" and "scheduler B") that coexist on the same system. The IBM-supplied APPC/MVS transaction scheduler, ASCH, is an example of such a scheduler.