HP3000/Image to Linix Red Hat/Oracle Back End

[Stephen Hulbert]

That's one horror story, but I'm sure it's not representative.
We moved from CISAM to Oracle on AIX and it just worked.
The main thing you have to remember is you're migrating a system not rewriting it.
1. You could spend a lot of time working out how to go from one key per table to as many as you want. Forget that, get your system working then worry.
2. Similarly with all the other shiny content a proper database offers. Don't spend any time writing triggers or stored procedures. Don't launch into using cursors. There'll be plenty of time for all that once you've got your system working. Although if your system is well-designed in Powerhouse already you won't need any.
3. The main problem, of course, is identity columns. However you do this it's going to be less efficient in data and/or code terms. This is unfortunately where you will need to write stored procedures. 
Originally we went with using sequences which avoids locking problems but doesn't guarantee contiguity. Now due to needing an arbitrary number of sequences per table we've moved back to last number tables. This guarantees contiguity but has locking issues. Use files are your friend in this. You can autogenerate them and you shouldn't need to go back and edit the files that use them if you do.
4. Oracle does not use zero dates. Powerhouse forces it to. However, if you ever want to use anything that isn't Powerhouse to access the data you should use the "default date is null" option on the PDL database statement. This stores null and reads zero transparently for default dates.
5. Oracle number types deal with decimal places transparently. That is number(12,2) has two decimal places in Oracle (e.g. 1.00) but is the integer you would expect in Powerhouse. (e.g. 100)
We went with number(12) and everything's fine. However, now that users are demanding ODBC access this and the zero dates mean we now have to write queries to provide it in a readable format.
Hope this helps,
Stephen.


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Stephen Hulbert
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Littlejohn LLP
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-----Original Message-----
From: powerh-l-bounces+shulbert=littlejohnllp.com at lists.sowder.com [mailto:powerh-l-bounces+shulbert=littlejohnllp.com at lists.sowder.com] On Behalf Of Richard Witkopp
Sent: 20 February 2012 19:37
To: powerh-l at lists.sowder.com
Subject: RE: HP3000/Image to Linix Red Hat/Oracle Back End

I was involved in a migration on VMS from ISAM files just to DEC Rdb, their relational database at the time. We were going to stay on the same operating system.

It was a huge project that lasted over three years that ultimately was a failure because the new system wasn't properly stress-tested. I would say that no matter how simple it may seem, (a switch to x86 Linux does not seem simple to me) it will take a lot more work than you expect. My suggestion would be to try to split off a minor subsystem that uses a couple dozen programs as a pilot project. That would tell you a lot about how the rest of the project might go.

-----Original Message-----
From: powerh-l-bounces+rwitkopp=phxa.com at lists.sowder.com [mailto:powerh-l-bounces+rwitkopp=phxa.com at lists.sowder.com] On Behalf Of Adrian Hudson
Sent: Monday, February 20, 2012 7:19 AM
To: powerh-l at lists.sowder.com
Subject: HP3000/Image to Linix Red Hat/Oracle Back End

Hi All,

We are currently in the early stages of planning a migration from
vanilla TurboImage and Powerhouse plus a handful of Cobol programs to
Red Hat Linux and Powerhouse with an Oracle backend.

I've already read some of the available documents, concerning
migration, from the IBM 'Cognos' site and, indeed, I've been involved
in several similar projects in the past, but never to Linux.

I'd just like the board to share any experiences/pitfalls/things to
look out for in a migration to Linux and I would also like anyone to
share their experiences of the tools available/methods to unload an
Image database and reload/perform data type migration into Oracle (or
any RDBMS).

Plus if anyone is available for Contract work in the South of the UK
(quite near Brighton) I would like to hear from them.

Best wishes to you all,


Adrian
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