RE: SQL logical file equivalent

Hi:

We use DDS-defined "reduced logicals", as described -- with a different
record format name and a specific, limited number of fields included --
for a variety of reasons. They are not only useful for avoiding level
checks, they also avoid reading unmanaged field values into a program. A
reduced logical with only a few fields selected from the physical, and
with all fields renamed in the program, can be used as a lookup table even
at a point where the base physical file (or another logical that sorts the
physical and includes all fields) has a completely different record
locked. That's just one example.

Darrell

Darrell A. Martin - 630-754-2141
Manager, Computer Operations
dmartin@xxxxxxxxxxxxx

midrange-l-bounces@xxxxxxxxxxxx wrote on 04/19/2007 07:29:08 PM:

"

But that's an important distinction. If you create a DDS LF and name the
fields those are the only fields in the lf, even if you add more to the
table. However, the LF created from an index will change automatically
to have any new fields in it. So if you're using that LF in a 3GL you
need to be worried about level checks.

One of the great things about SQL is the ability to add columns w/out
regard to level checks. Don't break that by using indexes in 3GL
programs for RLA.

"



But so will a regular logical file.



If I create a logical file over a physical file and just use the record
name equal to the record name of the physical file (which 99% of the
people do) and I add a field to the physical file using CHGPF , the
logical file will get the new field.

If I create the logical with record name different from the physical
record name and list the fields I want to include in the logical, and I
add a field to the physical using CHGPF, the new field will not show up.

So the behavior is no different if you go into operations navigator and
add a new field to a table. It will appear on the logical associated
with the index.

Of course, it makes no sense to me know days to use a logical or
physical record I/O unless I have to. I think this got started because
the person had a case tool that won't use SQL statements and has to have
a physical or logical file. Yuck!!



Probably 99% of my coding today is done using SQL.

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