APPC/MVS Server Facilities

With the addition of APPC/MVS server facilities in MVS/ESA SP 4.3, MVS/ESA strengthens its support for the client/server model of programming. APPC/MVS server facilities provide installations with the high-level-language callable services needed to write APPC/MVS servers (MVS-resident programs that can manage multiple LU 6.2 inbound conversations from multiple client TPs concurrently).

As of MVS/ESA SP 4.2, MVS/ESA provides scheduling support for LU 6.2 conversations between partner transaction programs. Inbound transaction program requests are scheduled for execution by the APPC/MVS transaction scheduler. (The installation can also supply its own transaction scheduler, if desired.) The APPC/MVS transaction scheduler provides two types of scheduling for transaction programs — standard and multi-trans. In both cases, the transaction scheduler processes inbound requests by running each requested transaction program in a subordinate address space called an initiator. While multi-trans scheduling provides better performance for frequently accessed transaction programs, both scheduling types are limited; no more than one inbound conversation can run in an initiator address space at a time.

APPC/MVS server facilities provide another way to process LU 6.2 inbound transaction program requests. Address spaces (started tasks, batch initiators, TSO/E users, or APPC/MVS initiators) can directly receive specific inbound requests, instead of requiring the transaction scheduler to process them. And, unlike scheduled TPs, these address spaces can receive multiple inbound conversations concurrently.