DOCUMENT:Q160884  13-JUN-2001  [sna]
TITLE   :SNA Server and "Bidirectional APPC" Support
PRODUCT :Microsoft SNA Server
PROD/VER:WINDOWS:2.0,2.1,2.11,3.0,3.0 SP1,3.0 SP2,3.0 SP3,4.0,4.0 SP1
OPER/SYS:
KEYWORDS:

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The information in this article applies to:

 - Microsoft SNA Server, versions 2.0, 2.1, 2.11, 3.0, 3.0 SP1, 3.0 SP2, 3.0 SP3, 4.0, 4.0 SP1, on platform(s):
    - the operating system: Microsoft Windows NT 
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SUMMARY
=======

APPC is a peer-oriented program-to-program API where either Transaction Program
(TP) can initiate a conversation. However, APPC / LU6.2 traditionally is
half-duplex, as defined by IBM in the LU6.2 "base option set". Under half-duplex
operation, once the converation is established, only one TP has direction to
send on a conversation at a time. The state of the conversation, as viewed by a
particular TP, governs which APPC verbs can be issued by the TP at a particular
time.

IBM now supports "full duplex" APPC where either program can issue both send and
receive verbs at the same time, as well as non-blocking APPC operation, which
are relatively new APPC option sets defined by IBM.

These option sets are:

112 -- Full-duplex conversations and expedited data
113 -- Non-blocking support

IBM defines these option sets in the IBM Transaction Programmer's Reference
Manual for LU Type 6.2 (IBM document number GC30-3084).

SNA Server does not support option set 112 or 113. SNA Server only supports
half-duplex operation, though either end can initiate the conversation. SNA
Server implements non-blocking support for APPC and CPIC API's for 16- bit and
32-bit Windows per the Windows APPC and CPIC specifications, though these
specifications do not follow the IBM-defined option set 113.

See Chapter 1 of the SNA Server Reference Guide for a list of LU6.2 option sets
supported by SNA Server.

Additional query words:

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Keywords          :  
Technology        : kbAudDeveloper kbSNAServSearch
Version           : WINDOWS:2.0,2.1,2.11,3.0,3.0 SP1,3.0 SP2,3.0 SP3,4.0,4.0 SP1

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