SNA DHCF enables IBM System 370-compatible mainframes and
series 900 HP 3000 systems to communicate interactively. Users of
IBM 3270 display stations with access to the IBM Host Command Facility
(HCF) can access an HP 3000 in an SNA network and initiate a session
on the MPE XL operating system. SNA DHCF converts ASCII data from HP
3000 VPLUS and TTY-compatible applications to the EBCDIC format
that IBM 3270 display stations require, and vice versa.
To avoid potential confusion, it is important to note that
IBM has a counterpart to Hewlett-Packard's SNA DHCF, which is called
DHCF.
System Connections |
 |
An IBM user can execute HCF commands to access an application
on a remote IBM minicomputer. If an IBM user wants to access an
application on a remote HP 3000 instead, he or she would use HCF
and HP SNA DHCF, rather than IBM DHCF. HP SNA DHCF emulates IBM
DHCF, enabling the connection of an HP 3000 to an IBM mainframe.
When SNA DHCF is used, an HP 3000 perceives an IBM 3270 display
station to be a virtual terminal (VT) device. Conversely, an IBM
mainframe perceives an HP 3000 to be a remote IBM minicomputer.
VPLUS Supportability |
|
SNA DHCF supports VPLUS applications if you recompile forms
files for use with IBM 3270 display stations. Certain IBM 3270 display
station limitations affect full-screen VPLUS applications. For instance,
the expanded HP terminal feature set offers display enhancements,
such as inverse video, that are unavailable on many IBM 3270 display stations.
Consequently, you cannot display these enhancements on an IBM 3270
display station when using SNA DHCF.
Applications must exclusively use VPLUS intrinsics for all
terminal I/O between VOPENTERM and VCLOSETERM calls, because the SNA DHCF subsystem is in unedited
mode when performing VPLUS I/O. Unedited mode means that the subsystem
expects valid 3270 data streams (in EBCDIC) from the VPLUS intrinsics.
If you design HP 3000 application programs with VPLUS-based
forms for IBM 3270 application users, or for both HP 3000 and IBM
3270 users, it is imperative to note the IBM 3270 display station
and forms compilation limitations described in subsequent sections
of this appendix.
