Expand Management Programming Manual
SPI PROGRAMMING CONSIDERATIONS FOR THE EXPAND SUBSYSTEM
Building the Command Buffer
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 will continue to work if it is compiled with new
definition files that add new fields to the token.
The only tokens that can appear more than once in an EXPAND
command are ZSPI-TKN-COMMENT, ZCOM-TKN-OBJNAME, and ZCOM-TKN-
TRACE-OPT. ZSPI-TKN-COMMENT is the comment token, described
in the
Distributed Systems Management (DSM) Programming Manual
.
ZCOM-TKN-OBJNAME is the object-name token, described in Section
6, "Common Definitions." ZCOM-TKN-TRACE-OPT is a token used in
the TRACE command, and it is described in Section 7, "Commands
and Responses."
If any of the other tokens in a command appear more than once, an
error is given either by the EXPAND subsystem or by SCP.
DISCONTINUING A COMMAND IN PROGRESS
General programming considerations for discontinuing a command
in progress are discussed in the
Communications Management
Programming Manual
.
The EXPAND subsystem does support the use of the token ZSPI-
TKN-ALLOW-TYPE, which allows an application to specify, in a
command operating on multiple objects, whether or not the EXPAND
subsystem should continue immediately to the next object if it
failed on the previous one. If no value is specified for this
token, the EXPAND subsystem continues to the next object only if
no errors or warnings occurred on the previous one.
When the EXPAND subsystem discontinues a command because of an
error or warning, it immediately sends a reply message to the
application. The reply message contains a context token. The
application can choose to resend the command, causing the EXPAND
subsystem to proceed to the next object, or to abandon the
command.
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