HP-UX SNAplus2 Upgrade Guide (August 2003)

Porting Application Programs
Overview of Porting Applications
Chapter 3 35
Overview of Porting Applications
The SNAplus2 API libraries have been designed to be
backward-compatible, and to include all the functions that were
available in the back-level software as well as new functions specific to
the current-level software. This means that, in most cases, when
upgrading from SNAplus no migration is required because the
application will automatically use the new shared libraries. When
upgrading from Release 5 to Release 6.0 or 6.1, you can run existing
applications without any change to the application. However, if you want
to add a new function, for example adding the TP Server for APPC, you
must extend the application and relink the program.
In many cases, the current-level API implements new functions using
VCB fields that were marked as “reserved” in the back-level API. If your
application sets all reserved fields to 0, as recommended, it will operate
with the new libraries with no change in function; however,
unpredictable results may occur if reserved fields are not set to zero.