HP 3000 Manuals

General Information Manual

Protecting Your Application Investment 

Within the HP 3000 family, simple upgrade paths are provided to
higher-performing systems.  Simple upgrades and return credits on older
systems mean that upgrades are cost-effective.  A simple backup and
restore procedure with object code compatibility means applications run
without changes or recompilation and without disrupting of your business.

Native mode and compatibility mode 

Hewlett-Packard ensures compatibility and provides a smooth migration
path when moving from MPE V-based HP 3000s to 900 Series PA-RISC systems.
MPE/XL is a compatible superset of MPE V.

Native mode 
Native mode, the native run-time environment of the 900 Series, offers
the highest performance on PA-RISC. In accordance with Hewlett-Packard's
design objectives, native mode on a PA-RISC system provides source code
compatibility with MPE V-based systems where appropriate.  A program
written on an MPE V system can simply be recompiled using a 900 Series
native mode compiler to take advantage of PA-RISC's performance benefits.

Native mode is the preferred environment because it makes full use of the
high performance of the 900 Series systems.  Native mode provides all the
benefits of MPE/XL described in this chapter, such as demand-paged
virtual memory, large address space, and mapped files.

Compatibility mode 
Compatibility mode provides object code compatibility between MPE V-based
systems and the 900 Series.  It does this by emulating in software the
MPE V HP 3000 environment on the 900 Series system.  Compatibility mode
allows current HP 3000 customers to move their applications and data to
the 900 Series systems without changes or recompilation.

Compatibility mode provides a working MPE V environment, including MPE V
code and stack structures and callable MPE V system intrinsics.  As a
result, compatibility mode also allows cross-development of MPE V
applications on 900 Series systems.

Flexibility and migration 

Compatibility mode and HP's assortment of migration utilities provide for
smooth, flexible migration to 900 Series systems.

Because of the high degree of object code compatibility, you can simply
store an MPE V program, restore it on a 900 Series system, and run it in
compatibility mode without modification or recompilation.  This applies
to applications written in any language supported by MPE V. You can move
your databases to the
900 Series in the same way.

For improved compatibility mode performance of MPE V object code, the 900
Series provides an MPE V object code translator that translates MPE V
object code into the native instructions of the 900 Series.  Translation
of the MPE V object code reduces the overhead incurred while running a
program in compatibility mode.

To take full advantage of the 900 Series performance and the benefits of
the new operating system, applications can be recompiled using native
mode compilers.  These compilers provide source code compatibility with
the rest of the HP 3000 family.  Typically, little or no code
modification is required.


          Figure 3-12.  Migration Flexibility Example 

Applications can run partly in native mode and partly in compatibility
mode.  The operating system switches between modes transparently.  This
transparency in operation is made possible by the switch subsystem, which
determines whether code is in native mode or compatibility mode and
automatically switches between modes as needed while an application is
running.

Native mode compilers are available for COBOL II, FORTRAN 77, C, Business
BASIC, Pascal, RPG, and Transact.

The figure above illustrates the flexibility of migrating to the
900 Series.  You can move some applications to native mode while leaving
others in compatibility mode.  As illustrated, the same database can be
accessed by programs in compatibility mode or native mode.

The total effect is that you can immediately move your applications to
compatibility mode and migrate your programs to native mode when and if
it fits your schedule.

In addition, if an application written in a high-level language calls
SPL/V procedures, it can be recompiled to native mode and call SPL/V
procedures in compatibility mode using a user-supplied mode-switching
procedure.

Exceptions 
Naturally, there are some minor restrictions in migrating MPE V-based
applications to the 900 Series.  For example, applications that use
undocumented intrinsics, execute in privileged mode, or use privileged
machine instructions may need to be modified in order to run on a 900
Series system.

For information regarding other, less frequently encountered exceptions,
please contact your HP sales representative.

Cross-development (MPE V and MPE/XL) 

Applications can be developed on a 900 Series system for use on other HP
3000 systems, allowing a 900 Series system to be used for centralized
application development.

The same source code for programs written in HP COBOL II/XL, HP FORTRAN
77/XL, and HP Pascal/XL can be compiled to run in native mode on a 900
Series system and on MPE V-based systems.

The same source code written in COBOL II/V, HP FORTRAN 77/V, Pascal/V, HP
FORTRAN 66/V, HP BASIC/V, HP Business BASIC/V, HP RPG/V, and HP SPL/V can
be compiled to run in compatibility mode on the 900 Series or on MPE
V-based systems.  The MPE V segmenter is supplied with the HP 3000 to
facilitate cross-family development in these languages.

MPE/iX 5.0 Documentation