Re: Are level checks still useful?

[Scott Klement <rpg400-l@xxxxxxxxxxxxxxxx>]

Dale,

Most likely, you have LVLCHK(*NO) on the PF, but LVLCHK(*YES) on LFs 
that are read by the programs.

The reason you don't have level checks in PHP (and similar environments) 
is because they don't have hard-coded from/to positions in fields in the 
record.  When you compile an RPG program, the compiler reads the 
external definition, and hard-codes the from/to positions of fields in 
the record into the program.  You have to recompile for it to update 
these -- and therefore, level checks are an important safeguard. Without 
them, if the file changes, you'll end up reading (or worse, writing) 
incorrect data at incorrect places in the record, causing a big huge mess.

If you don't like getting the errors, eliminate all your F-specs. 
Instead, use SQL to read all files, and read into program-defined 
variables (don't use an external definition for the variables you read 
into.)  Then you will eliminate level check errors, making your RPG 
program work the same way the PHP programs do.

-SK



On 11/1/2012 8:17 AM, dale janus wrote:
> We are in the slow, gradual process of changing from DDS to DDL.
> Actually, we are creating new files with ops navigator and usually not
> keeping the create specs.  We just use navigator to change the file when
> needed. Mostly we need record ID and timestamp, or date fields added.
>
> But we have lots of old files.  Yesterday, we needed to add 2 fields to a
> file (a timestamp and a record id, both added with DDL in ops nav.)
> Since we are adding the fields to the end of the files, we figured this
> would be a good time to remove level check from the file.  But it did not
> work.
>
> Here is our process for adding new fields to a file.  We have a library
> that contains all our RPG, DDL, CL etc. but no data.  We add the new
> fields to the file (called DIRECT).  We change to level check *no.  This
> creates an empty file with the new fields.
>
> We write a CL program to copy the data from production library to empty
> library using CPYF with *nochk.  Then in the production library we delete
> all the logicals, rename the existing file to DIRECTOLD.  Next CPYF from
> the empty library file (now filled with production data and new fields)
> to the production library, CRTFILE(*YES) then recreate the logicals.
>
> When checking with DSPFD, both the file in the empty library and
> production library say:
>    Record format level check . . . . . . . . . : LVLCHK     *NO
>
> Yet when I run programs against the file DIRECT or its logicals, I get
> level check CPF4131errors.
>
> So I had to recompile all the programs anyway.
>
> We are a small shop with just 2 of us.  We write all our own code, so we
> are quite sure that adding fields to the end of a record will not affect
> old programs.
>
> I am RPG guy, my associate is PHP/WEB guy.  He just kind of rolls his
> eyes at me when I jump through all these hoops to add fields.  His PHP
> programs just keep on rolling, no matter what the file looks like.
>
>
>
> So this long discourse asks two questions.
>
> Why do my RPG programs (some RPG III, some ILE) insist on level check
> when the file says LVLCHK *NO?
>
> And
>
> Is level check still useful?  The ability to quickly add fields to files
> seems to outweigh the comfort of your rpg programs knowing exactly what
> the file looks like.  Especially when half (uhh, maybe not half but lots
> of them) of your programs are PHP.
>
> ---Dale