Guardian Application Conversion Guide

New System Messages
Conversion Concepts
2–16 096047 Tandem Computers Incorporated
Null Process Handle
A null process handle contains a -1 in each of its ten words. It is used for the following
purposes:
An application can specify a null process handle (for example, by using the
PROECSSHANDLE_NULLIT_ procedure) as an input parameter in a D-series
procedure such as PROCESS_GETINFO_ in order to get information about itself.
Some D-series procedures return a null process handle to represent a nonexistent
process (for example, a backup-process parameter when a backup process does
not exist).
An application can use a process handle as a place holder for a nonexistent
process. When an application declares a process-handle variable, it can initialize
the variable to a null value. If a server process monitors its openers, it can set the
primary and backup process-handle fields in an opener table entry to null values
as place holders for the nonexistent processes.
If a server process uses the OPENER_LOST_ procedure, it must set any unused
process-handle fields in its opener table to null values. See Section 3, “Converting
TAL Applications,” for more information about defining an opener table for the
OPENER_LOST_ procedure.
New System Messages The D-series operating system provides new user-level system messages that a
converted application can read from $RECEIVE. (An application that does not open
$RECEIVE to request system messages need not be concerned with system messages.)
An application that uses C-series Guardian procedures will also continue to receive
C-series system messages.
Some D-series messages supersede one or more C-series messages, while other
D-series messages support new procedures or features. For example, the D-series -101
(Process deletion) message supersedes the C-series -5 (Stop), -6 (Abend), and -2 (CPU
down for a named process deletion) messages, while the D-series -109 (Nowait
FILENAME_FINDNEXT_ completion) message supports the new
FILENAME_FINDNEXT_ procedure.
Tandem provides structure declarations that you can use in your application to read
and process system messages. Tandem uses the ZSYSDDL file to generate the
ZSYSTAL, ZSYSCOB, ZSYSC, and ZSYSPAS files for TAL, COBOL85, C, and Pascal
applications, respectively. To use the ZSYSDDL declarations, include the appropriate
file (or sections of the file) in your source code.
For a table of C-series messages and the D-series messages that supersede them, refer
to Appendix B, “System Messages.” For the format and description of all system
messages, refer to the Guardian Procedure Errors and Messages Manual.