Re: Should I replace all CHAIN, SETLL, and READs to SQL

On 11/2/2012 4:12 PM, Alan Campin wrote:

As to the I will just recompile that's great if you have 5 day a week shop and can spend hours on the weekend recompiling 5000 programs because you added a field to the customer master but if you are running a 7 x 24 operation they frown on that. The bottom line is the same. Every shop I have ever been in nobody wants to recompile the world. I work in Java shop for new development (Not me unfortunately) but you watch every day they are changing the database and nobody even thinks about. Every AS/400 shop. Absolute agony about making a change to a table.

Changing a table is not something to be undertaken lightly, but it's also not a nightmare. In my opinion if I'm making regular changes to a master file being used by thousands of programs, then I've really fallen asleep at the wheel in design changes. But that's neither here nor there - making a database change can be quite easy if you just do a little prior preparation.

A lot of this can be done with smart architecture. If you have dynamic control of the user's library list, then the maximum downtime required for a full changeover is however long it takes to copy the file from one version to another. Sign everyone off, copy the file, change the library list, let them sign back on.

Add a database trigger to keep the files in sync and you don't even need simultaneous signoff. In fact, you can have people in both environments at the same time (we borrow this "drain-over" technique from high availability sites).

In any case, if you know how to use the midrange platform database changes are little more difficult than any other implementation where you have to install new versions of many programs at the same time. And I don't care what database access technique you use, you will have situations where multiple programs need to be updated simultaneously.

Joe