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.
midrange.com
