Re: LVLCHK *NO -- RPG400-L

Thanks Alan!

If I understand your sample correctly, all that RPG code was generated by
the pre-compiler. What I don't see is the data structure definition. When
and by whom is that defined? Does the definition contain field sizes and
types?

>From what you know, how close is this to what's been discussed about dynamic
file linking? It sounds pretty close to me so far. And if that's so, then I
have to agree that for NEP's and other long-running programs, the
"mini-compile" at run time has to be insignificant. IMHO, it's probably
insignificant in an interactive program running on a reasonably fast RISC
box.

In other words, why not build that in to RPG instead of having to use SQL
syntax and a pre-compiler? Maybe an SQL-function file instead of a
Full-function file. What do you think?

Peter Dow
Dow Software Services, Inc.
909 425-0194 voice/fax


----- Original Message -----
From: Alan Campin <Alan.Campin@CaseLogic.com>
To: <RPG400-L@midrange.com>
Sent: Tuesday, October 05, 1999 6:19 PM
Subject: RE: LVLCHK *NO


> Peter wrote:
> >> How much does it take to process a dynamic SELECT statement?
>
> With SQL in an RPG program, 99% of the time you are not issuing Dynamic
SQL.
> The only reason you would do so is if you did not know what the SQL
> statement is going to be at compile. The norm is to enter the SQL
statement
> and associate it a data structure. One element per field in the select
> statement. The precompiler just takes what you have defined and turns it
> into dynamic calls to a SQL program that does the I/O but the SQL is
already
> precompiled and the AS/400 has to only execute the access plan. (Note that
> the AS/400 still has to do a mini-compile to get the location of the data
in
> the table each time the program runs.) When the precompiler finishes, you
> have regular RPG and the RPG compiler is called. All languages where SQL
is
> not built in work this way. Here is what it looks like after compile. Note
> that the SQL statement is just comments.
>
>   *-----------------------------------------------------------------
>   * Declare SQL to read IVCTRL records.
>  c*exec sql
>  c*  declare c1 cursor for
>  c* select icinvn,ictypp,icinyy,icorno,icdupf,icpape
>  c*  from ivctrl
>  c*  where icreq# = :x0req# and
>  c*        ictypp = :x0typp and icedii = :x0edii
>  c*  order by icinvn for update of icreq#
>  c*end-exec
>   *-----------------------------------------------------------------
>   * Open SQL cursor.
>  c*exec sql
>  c* open c1
>  c*end-exec
>
>  C                   EVAL      SQL_00004  = X0REQ#
>  C                   EVAL      SQL_00005  = X0TYPP
>  C                   EVAL      SQL_00006  = X0EDII
>  C                   Z-ADD     -4            SQLER6
>  C     SQL_00002     IFEQ      0
>  C     SQL_00003     ORNE      *LOVAL
>  C                   CALL      'QSQROUTE'
>  C                   PARM                    SQLCA
>  C                   PARM                    SQL_00000
>  C                   ELSE
>  C                   CALL      'QSQLOPEN'
>  C                   PARM                    SQLCA
>  C                   PARM                    SQL_00000
>  C                   END
>
>
>  c                   dou       sqlcod <> 0
>  c*exec sql
>  c*  fetch c1 into :zsin                               <<< Note the data
> structure name.
>  c*end-exec
>  C                   Z-ADD     -4            SQLER6
>  C                   CALL      'QSQROUTE'
>  C                   PARM                    SQLCA
>  C                   PARM                    SQL_00007
>  C     SQL_00010     IFEQ      '1'
>  C                   EVAL      ICINVN = SQL_00011
>  C                   EVAL      ICTYPP = SQL_00012
>  C                   EVAL      ICINYY = SQL_00013
>  C                   EVAL      ICORNO = SQL_00014
>  C                   EVAL      ICDUPF = SQL_00015
>  C                   EVAL      ICPAPE = SQL_00016
>  C                   END
>
> We use SQL for almost all of our new batch or server programs because of
the
> greater efficiency. There is a cost but especially in a never ending batch
> program, it becomes unimportant and, of course, we never have to touch the
> program if we maintain the table.
>
> Peter wrote:
>
> >> ??If RPG were modified to dynamically link files, would
> >> the definition happen at compile-time or run-time?
>
> The compile time processing would still occur as normal. The difference is
> that at run-time, the AS/400 goes out and looks up the file format, and
> determines what the starting positions are for each variable you are
reading
> in. In effect, a mini-compile.
>
> A dynamic SQL is very expensive so you only use them in cases where you
have
> to.
>
> Hope this is helpful.
>
> -----Original Message-----
> From: Peter Dow [mailto:pcdow@yahoo.com]
> Sent: Tuesday, October 05, 1999 3:44 PM
> To: RPG400-L@midrange.com
> Subject: Re: LVLCHK *NO
>
>
> > Okay, so the gist of this is, it would take too much time and processor
> power
> > to dynamically link the files, and you think we want the extra check at
> run time.
>
> > The main advantage to static linking is the system can open the programs
> faster,
> > and the program won't run if it fails the level check.  Although I think
> that the way
> > RPG shotguns memory locations for files may come into play also.
> >
> > Has anyone ever did a test on the added time and processor needed to be
> able
> > to link database files dynamically on the AS/400?
>
> I've seen several postings in this list nudging us towards using SQL in
our
> RPG programs, and none of them complain about time and processing power.
How
> much does it take to process a dynamic SELECT statement? Also, how many of
> us use some file utility such as DBU, VIEW or even the lowly UPDDTA? All
of
> these obtain the field list for the file and format it for us, and while
it
> may take a second or two longer, I for one am not complaining. And how
much
> time are we talking about anyway? Minutes? Seconds? Subseconds? If we're
> talking about a program that prints a report from thousands or millions of
> records, what is that percentage-wise?
>
> OTOH, there's the consideration of what this would do to RPG. I haven't
used
> SQL with RPG yet, so I'm not familiar with how variables are defined, but
> since the manual talks about a pre-compiler it's probably done from the
> external definition. If RPG were modified to dynamically link files, would
> the definition happen at compile-time or run-time? If it happens at
> run-time, things could get really interesting (does EVAL A = B + C mean
add
> two numbers or concatenate two strings? would this be determined at
> run-time?)  If it happens at compile-time, that means some more checking
at
> file open time to determine if the fields not only have the same name, but
> the same type and precision.
>
> Maybe some of you people that use SQL with RPG could give us some hints on
> what it would be like to have dynamically linked files built into RPG.
>
>
> >
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