Re: Fw: Are level checks still useful?

[Gqcy <gmufasa01@xxxxxxxxx>]

> > Make sense?


Yes Scott,
you talked me off the edge.

When I describe the situation as you pointed out, putting a new field in 
between other existing fields, or lengthening or changing a field type, 
 my PHP (non-RLA) brothers will say.... "who would be dumb enough to do 
that!?"

again,
I am stuck between the "management" of the system i developers saying 
the opportunity of failure is too high if we change existing dds files,
and the open mocking from the php group on our arcane, pre-database 
database.





On 11/1/2012 3:51 PM, Scott Klement wrote:
> On 11/1/2012 3:39 PM, Gqcy wrote:
> > O, this appears to be a religious argument.
> > I was thinking there were actual reasons against turning off level check.
>
> RPG hard-codes the field positions in the record. So if you start out
> with a file like this:
>
> A R MYREC
> A FIELD1 10A
> A FIELD2 9P 2
> A FIELD3 3A
>
> That means that field1 occupies positions 1-10, field2 occupies 11-15,
> field3 occupies 16-18.
>
> If you then change your file to look like this:
>
> A R MYREC
> A FIELD1 10A
> A FOO 1S 0
> A FIELD2 9P 2
> A FIELD3 3A
>
> the positions of FIELD2 and FIELD3 are now one position different. With
> this change they are in positions 12-16 and 17-19, respectively. But,
> until the RPG code is recompiled to pick up the new definitions, it'll
> still try to read/write them from positions 11-15 and 16-18, because it
> doesn't know that they have changed.
>
> A "record format level check" (LVLCHK) is to protect you against reading
> garbage data (part of one field, part of another) when reading, and
> worse, overwrite part of one field with part of another when writing.
>
> With LVLCHK(*YES), RPG will get a level check error, and the programmer
> will know that he has to recompile his program. If he forgets or a
> program gets missed, it continues to get the error, which is better than
> corrupting the data.
>
> Make sense?
>
> However, it's not really like russian roulette, which was a bad analogy.
> After all, we in the RPG community lived with program-described files
> for many years. It wasn't as nice, but it wasn't like we were constantly
> dying from gunshot wounds, either. You just had to be more careful,
> that's all. The same is true of LVLCHK(*NO). It's not "pure concentrated
> evil", but rather, you just have to be more careful.
>
> IMHO, it's just not worth it (except maybe temporarily, if you have a
> very small upgrade window). It's just not that hard to recompile
> everything.
>
> And if you /want/ to eliminate level checks, using SQL is a much better,
> cleaner, safer way to go about it than simply turning off LVLCHK.