TS/MP 2.5 Management Programming Manual

Figure 6 Sending Commands and Receiving Responses
For a detailed description of how to build command messages and decode responses, see “SPI
Programming Considerations” (page 29). Details on the SPI procedures and their use with various
languages are available in the SPI Programming Manual.
Design Considerations
Consider these points when designing, configuring, and securing a management application that
sends commands to and receives replies from a Pathway subsystem:
• The PATHMON process does not support multiple outstanding requests from the same program.
Only one NOWAIT I/O operation is permitted for each opener.
• Pathway subsystems do not support cancellation of outstanding commands (that is, an
asynchronous command abort).
If an application calls the CANCEL or CANCELREQ procedure to cancel requests to the
PATHMON process, only the reply is cancelled if the PATHMON process has already read
the command message (that is, the cancellation is partial). The PATHMON process executes
the command and issues a reply, which the operating system then discards. The command is
cancelled, if the PATHMON process has not yet read the command message. However, the
application cannot determine whether the command message is read. If a new request is sent
to the PATHMON process before it has completed processing a previous cancel request, then
error 28 is returned.
Use CANCEL or CANCELREQ only if the application to monitoring is unimportant, regardless
of whether the command was performed.
• Pathway subsystems do not support the ALLOW-TYPE token or the RESPONSETYPE token.
• The PATHCOM MAXSPI parameter, which you set during the Pathway subsystem startup and
you can change only by stopping the Pathway subsystem, establishes the maximum number
of user-written processes that can simultaneously open an interface to a Pathway subsystem.
In the Management Programming interface, ZMAXSPI is a field in the ZPWY-DDL-DEF-PATHWAY
data structure.
The value you give for ZMAXSPI can range from 1 to 100. Until the Pathway subsystem is
started, only one process using SPI or one PATHCOM process can open the PATHMON
process.
Design Considerations 27