Database migration

Daryl Tester Daryl.Tester at
Mon Dec 2 23:28:18 CST 2002

Andrew Reid wrote:

> At this stage, I'm particularly interested in hearing about people's
> experiences and recomendations when it comes to database servers. I've
> been thinking PostgreSQL from the Open Source world, and probably
> Oracle from the commercial world, as options.

Both of these are robust databases with their own peculiar wrinkles;
it's be worth getting A DBA to look over your in-progress/final system
to see what performance tuning might be applicable (I've been bitten
by a Postgres peculiarity recently that's going to involve some
system reengineering on my part).

> My knowledge of Btreive is fairly minimal (and I'd like to keep it
> that way, thank-you-very-much), so I thought I'd ask: has anyone had
> any experience in moving data out of Btrieve and into a more
> heavy-duty SQL server like PostgreSQL or Oracle?

I've done a DBase to Postgresql (6.5ish) conversion a while back.  I
used Python to validate read and validate the database, then wrote it
to a staging area (I can't remember if that version supported
referential checking, but I do remember spending a while on it). 
Then the next phase involved restructuring the schemas.

> How much hair do you have left?

Most of it.  Not the same colour, though.

> If anyone has any general comments and/or ramblings, please; I'd love
> to hear from you. It makes it look as though I'm doing something,
> which pleases my boss ;-)

In no particular order:

1) Plan it, and well.
2) Have backout procedures (in case it goes pear-shaped).
3) If able to, run the systems in parallel (with phased cutover).
4) Never make changes on a Friday afternoon (especially on a system
   that's used on a weekend).
5) Time a subset of your data import, so you can predict how big a
   window you will require to do the real import (related to 1).
6) (related to 5) Leave the indexes off when doing the import!
   The number of times I've seen this in the real world ... sheesh

How are you going to get the existing Windows clients to talk to the
new database?

I'm sure other stuff will come to me in the middle of the night ...

  Daryl Tester,  Software Wrangler and Bit Herder, IOCANE Pty. Ltd.

"Hey ho Mr. Krinkle, have you heard the brand new sound?
 It's a cross between Jimi Hendrix, Bocephus, Cher and James Brown.
 It's called Heavy Hometown New Wave, cold-filtered, low-calorie dry." - Primus

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