The Set_AS_Attributes service lets a transaction scheduler set attributes for a subordinate address space. In particular, this service can set an attribute to designate whether conversations allocated from the specified address space are to be associated to the system base LU. You can use this service to prevent an inadvertent association in cases where the subordinate address space allocates a conversation before the transaction scheduler connects the subordinate address space to itself. Without Set_AS_Attributes in such cases, the conversation is assigned to the system base LU, and when the transaction scheduler attempts to connect the subordinate address space to itself later, if the conversation is still outstanding, the connect fails.

For example, you could use Set_AS_Attributes for this purpose in the following manner:

1. The transaction scheduler is active when APPC is not, so Identify and Connect cannot be performed.
2. The transaction scheduler calls Set_AS_Attributes with the Default_LU_Designation parameter set to 1 (to not associate conversations with the system base LU).
3. APPC is started on the system.
4. A subordinate address space allocates a conversation before the transaction scheduler identifies itself to APPC and connects the subordinate address space.

In the above scenario, if the transaction scheduler did not call Set_AS_Attributes first, APPC/MVS would assign the subordinate address space to the system base LU as soon as APPC/MVS received the outbound allocate request.

Instead, because the transaction scheduler does call Set_AS_Attributes first, APPC rejects the allocate request. When the transaction scheduler is notified of APPC initialization, the transaction scheduler can identify itself to APPC and connect the subordinate address space to itself.

The Set_AS_Attributes service can be called when APPC/MVS is not active.

CALL ATBSASA (ASCB_ptr, 
              Default_LU_Designation, 
              Return_Code
             );