MS-DOS Considerations

This topic summarizes information about developing TPs for the Microsoft® MS-DOS® system.

AS/400 PC Support Router API
MS-DOS support for Windows APPC is handled in one of two ways:

For additional information on the PC Support Router API, see the IBM PC Support/400 Application Program Interface Reference, part number SC41-8254.

CSV restrictions when SnaBase is not loaded
If your application is running on an SNA Server Windows-based client or MS-DOS-based client, and SnaBase has not been loaded, only the following verbs are available:

GET_CP_CONVERT_TABLE

CONVERT

Under these circumstances, CONVERT cannot use a type G conversion table. Attempting to use a type G conversion table causes the system to return the sv_table_error primary return code.

Attempting to issue COPY_TRACE_TO_FILE, DEFINE_TRACE, LOG_MESSAGE, or TRANSFER_MS_DATA causes the system to return the sv_comm_subsystem_not_loaded primary return code.

Limits
Additional system limits are described in the Microsoft SNA Server Administration Guide.
Link library
The link library for APPC is DOSACS.LIB.
Packing
VCBs are not packed. As a result, DWORDs and WORDs are on WORD boundaries, and BYTEs are on BYTE boundaries. This means, for example, that there is not a 2-byte gap between the primary and secondary return codes. VCBs should be accessed using the structures provided, and compiler options that change this packing method should be avoided.
Partner TPs
SNA Server invokable TPs cannot be run on MS-DOS-based clients. No support is provided for autostarting MS-DOS partner TPs. The call-level interface contains the same syntax as that of OS/2.
RECEIVE_AND_POST and MC_RECEIVE_AND_POST
These verbs are not available with MS-DOS.
Simultaneous conversation
In an MS-DOS environment, a TP can participate in as many as 16 conversations simultaneously.
SnaBase
When running a TP on an SNA Server MS-DOS-based client, you must use SnaBase, which supports APPC. If you attempt to use something other than SnaBase, your TP will not run.