Upgrading to OpenVMS I64 and Integrity

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http://64.223.189.234/node/457

Submitted by Hoff on August 7, 2007 - 16:41.

Tagged: C • OpenVMS • OpenVMS Alpha • OpenVMS I64 • OpenVMS VAX • Porting • Programming • Servers

know your code and path
alpha to integrity
many ways one hath

There is no single best way to port your application code from OpenVMS VAX to OpenVMS Alpha over to OpenVMS I64 and Integrity servers and Intel Itanium processors.

Some code is a straight compile, and some requires a little more effort, and some architecture-dependent or inner-mode code just won't port easily.

The following assumes user-mode code, and the availability of prerequisite layered products.

When you are upgrading from OpenVMS VAX or OpenVMS Alpha, it works best to get to the most current available compiler versions as a prerequisite to starting the port to Integrity. This helps avoid confusing issues of latent coding bugs and compiler changes with platform changes.

You will also want to ensure your code builds correctly on OpenVMS VAX or OpenVMS Alpha, and using moderate syntax checking as available.

Porting code that uses relaxed syntax checking — VAX C code or code compiled with CC /STANDARD=VAXC, for instance — is more involved and more effort, and errors can be subtle. Using stricter syntax checking and/or tools such as lint can help isolate and exterminate errors earlier in the process. Older code can and often will have latent bugs. Newer compilers can include better syntax checking, or updated language standards.

Once you have the same or similar compiler and layered product versions, use of a cluster can help speed the port as you can work from common code. You can use the same DECset CMS libraries, for instance. If you can't work with a cluster, then Subversion or CVS ports are available for OpenVMS, and can help keep a lid on the code changes and code version issues.

When looking at the operating system version, there can be more flexibility. With OpenVMS VAX, anywhere from V6.0 and upwards is basically the same operating system software. With OpenVMS Alpha, anything from V7.3-2 and upwards is quite similar, but it's best to get to the most current or to the same OpenVMS versions where you can manage it.

Compiler and layered product upgrades can require OpenVMS upgrades. (Upgrade paths: [Alpha], [Integrity], [VAX]) Clustering too can require OpenVMS upgrades.

The biggest rational for having the same or similar OpenVMS version and for OpenVMS upgrades is when you want to use the same code on both platforms; where you want to have and use common code. And even should the application port is intended to be one-way, this is a good idea as it provides an escape hatch should the application port have problems initially coming on-line. This provides a fall-back.

For related discussions here at HoffmanLabs, see Porting Applications onto OpenVMS I64 and Porting Applications Off of OpenVMS. Also skim Porting Applications from HP OpenVMS Alpha to HP OpenVMS Industry Standard 64 for Integrity Server in the OpenVMS documentation set.