AM3270 Management Programming Manual

SECTION 4
SPI PROGRAMMING CONSIDERATIONS FOR AM3270
The Communications Management Programming Manual discusses gen-
eral programming considerations for writing applications that
use the Subsystem Programmatic Interface (SPI) to communicate
with data-communications subsystems like the AM3270 subsystem.
This section discusses SPI programming considerations that are
specific to the AM3270 subsystem.
BUILDING THE COMMAND BUFFER
The following programming considerations apply when an applica-
tion builds the command buffer for an AM3270 command.
The recommended buffer length in bytes for a command is a
predefined value with the symbolic name ZCOM-VAL-MAXBUFLEN.
The subsystem does not support multiple commands in a single
request message. However, some of the commands can contain the
subordinate-modifier token, so one command can affect multiple
objects.
The subsystem does not support continuation of a command across
multiple messages, but it does support the special case of
receiving multiple reply messages using the context token, as
described in the Distributed Systems Management (DSM) Programming
Manual .
The command buffers for all commands can contain extensible
structured tokens. An extensible structured token that is to
appear in a command should always be initialized by the SPI
procedure SSNULL to ensure that every field of the token is
initialized to its null value. This action is important because
an operation will be performed if a field contains a value other
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