X25AM Management Programming Manual

X25AM Management Programming Manual—528037-001

4-1

SPI Programming Considerations for

the X25AM Subsystem

The SPI Common Extensions Manual discusses general programming considerations

for writing applications that use the Subsystem Programmatic Interface (SPI) to

communicate with data communications subsystems like the X25AM subsystem.

This section discusses SPI programming considerations that are specific to the X25AM

subsystem. Topics covered in this section include:

Building the Command Buffer

The following programming considerations apply when an application builds the

command buffer for an X25AM command.

The recommended buffer length in bytes for an X25AM command is a predefined value

with the symbolic name ZX25-VAL-BUFLEN.

The X25AM subsystem does not support multiple commands in a single request

message. However, many of the X25AM commands either accept more than one

object name in one command or can contain the subordinate-modifier token, so one

command can affect multiple objects. All the objects whose names appear in one

command must be of the same object type.

The X25AM 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 SPI Programming Manual.

The command buffers for all X25AM 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 than its null value. For example, in the

ALTER LINE command, if a field of the extensible structured token that describes the

line attributes contains a value other than its null value, that value is assigned to the

attribute corresponding to that field. Using SSNULL is important even when every field

of an extensible structured token will have a value assigned to it, so that the application

Topic Page

Building the Command Buffer

4-1

Discontinuing a Command in Progress 4-2

Receiving and Decoding the Response Buffer 4-2

Error Handling 4-3

Security 4-3