Migration from OpenVMS(DCL Scripts) To Linux(Python) (216 Views)
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Occasional Visitor
pks_2
Posts: 1
Registered: ‎02-08-2010
Message 1 of 5 (216 Views)

Migration from OpenVMS(DCL Scripts) To Linux(Python)

Hi guys,

what is the major key word/point need to be kept in mind at the same time when planning to migrate from OpenVMS(DCL Scripts) To Linux(Python)

Note: Please share your exp if any buddy has involved in the same kind of activity ever.
Honored Contributor
labadie_1
Posts: 1,221
Registered: ‎08-07-2003
Message 2 of 5 (216 Views)

Re: Migration from OpenVMS(DCL Scripts) To Linux(Python)

VMS is (usually) case-insensitive, while Linux is case-sensitive.

You can try to rewrite your Dcl scripts in Python for VMS, and then, the remaining work will be easy, compared to a DCl to bash conversion.
Honored Contributor
Hoff
Posts: 4,944
Registered: ‎01-29-2006
Message 3 of 5 (216 Views)

Re: Migration from OpenVMS(DCL Scripts) To Linux(Python)

1: This "port" is a complete rewrite; there's no mapping of DCL commands and lexical functions to bash and Python. I don't recommend an intermediate port here; going from DCL to Python and GNV and DCL on OpenVMS. Port the code. All the way. Otherwise, you're just going to be untangling your Python and GNV code to get all the way over to Linux; GNV is fairly limited, and has its share of oddities.

2: You're asking the wrong folks for help here. You want and centrally need to ask the folks that are familiar with and that know how to use Linux and bash and python. You're designing for a wholly new environment, and force-fitting an OpenVMS design or an OpenVMS solution or OpenVMS DCL structures will be somewhere between problematic and a maintenance headache and outright failure.

3: Google is your friend.

http://www.google.com/search?q=site%3Aitrc.hp.com+port+dcl+bash

http://labs.hoffmanlabs.com/node/225
Honored Contributor
John Gillings
Posts: 2,994
Registered: ‎07-31-2003
Message 4 of 5 (216 Views)

Re: Migration from OpenVMS(DCL Scripts) To Linux(Python)

>what is the major key word/point

OpenVMS is not Linux, Linux is not OpenVMS. DCL is not Python, Python is not DCL.

Some things are easy to do on OpenVMS and hard on Linux, other things are easy to do on Linux, but hard on OpenVMS. Similarly for DCL and Python, (or Perl, or C, or C++).

Typically DCL is different enough from scripting languages in the Unix world, that there's very little point in attempting a one for one translation. Much better to step back, look at the function of the procedure, and reimplement it in "the way" of the target system. Attempting to force fit OpenVMS ways of doing things is a path to frustration and failure.

(I've reimplemented some DCL procedures in Perl, halving the size and improving the run time 10 fold, just because the function is suited to Perl's strengths. Other DCL procedures in Perl can very difficult, slow, or just don't make sense).
A crucible of informative mistakes
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MarkOfAus
Posts: 170
Registered: ‎01-08-2007
Message 5 of 5 (216 Views)

Re: Migration from OpenVMS(DCL Scripts) To Linux(Python)

We did a DCL to Solaris sh/perl conversion a while back. The biggest issue, as the others have described are the inherent differences in the OS architecture. Linux has no idea of logicals, no idea of symbols, so you have to create adaptations for these two, at least.

Even the use of batch queues can be substituted with diligent use of "at" or a special cron account. Won't be exactly the same, of course, but it will suffice.

No doubt the logic inside a DCL script can be ported to Python, but the interaction with the OS is the most important (and difficult) aspect.

As Hoff says, you need to take this "project" and start from scratch, pulling apart each DCL script and seeing how it can be transposed onto Linux. If you don't you will go nowhere; fast.

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