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The Question is:
We are planning to migrate a host of existing application on VAX / OpenVMS on
to Alpha/OpenVMS for one of our clients. The applications are in VAX C,
Cobol, Pascal. Can to refer us to the manuals we need to understand the
possiblities of improving the c
ode performance (Optimizing the C & Cobol) to fully utilize the capabilities of
Alpha/OpenVMS.
The Answer is :
Your particular client likely has access to direct technical assistance
from Compaq, as well as various technical and managerial and migration
contacts here in OpenVMS Engineering -- please seriously consider using
more formal channels for this OpenVMS Alpha migration assistance.
That said...
First, please move to current versions of the products (compilers,
OpenVMS) on the OpenVMS VAX system. Then move to OpenVMS Alpha.
This two-stage port can simplify the migration process, as it separates
the compiler and OpenVMS differences from the architectural differences.
Then seriously consider configuring a cluster consisting of the OpenVMS
VAX system(s) and the new OpenVMS Alpha system(s) -- this greatly
simplifies the operations, permitting both platforms to access the
same application data and application source and system configuration
files, and permitting an incremental migration. Given your client's
business, it would typically work best to have these clusters set up
seperately from the production environment, in order to complete and
verify the port before (intentionally or otherwise) going on-line with
the application in the OpenVMS Alpha environment.
And as for your request for assistance in optimization, first get the
code running. Then look to optimize it, if necessary -- you will have
wholely new versions of the code generators, and the move from a ten
year old C compiler on VAX to a current-generation C compiler on
Alpha will likely see some improvements in the generated code. As
your particular client is also targeting a migration to recent Alpha
systems, you can also look to generate code specific to EV56 (typically)
to acquire access to Alpha extensions such as byte-word instructions.
(You could also generate the code for EV6, but in the experience of the
OpenVMS Wizard the byte-word is often the biggest single win.)
Also make CERTAIN you familiarize yourself with the differences and
enhancements -- Compaq C has seen many changes since VAX C. OpenVMS
has also seen many changes since your VAX C code was likely written.
please see the FAQ for the basics of operating with C on OpenVMS Alpha,
and for topics such as correctly setting VOTES and EXPECTED_VOTES values
in your development/migration cluster.
Topics 2055, 3036, and 4278 reference migration, and will be of some
interest in your effort.
Information on moving from VAX C to Compaq C on OpenVMS VAX is included
in the Compaq C for OpenVMS VAX documentation. Other relevent information
is included in the OpenVMS documentation set. And of course you may also
be able access at least some of the Compaq resources available to your
particular client.
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