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OpenVMS VAX to OpenVMS Alpha migration (take III

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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

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.

answer written or last revised on ( 17-JUL-2000 )

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