• Subject: RE: Logicals?
  • From: "Cotes, Steven" <cotess@xxxxxxxxxxx>
  • Date: Mon, 3 Nov 1997 11:51:57 -0800

> ----------
> From:         Buck Calabro[SMTP:mcalabro@commsoft.net]
> Sent:         Monday, November 03, 1997 6:06 AM
> To:   Midrange-L
> Subject:      RE:Logicals?
> >>Good day to all;
> >>I am wondering about using logical files; say I have a logical built
> >>over a large file and we need another logical which is very close to
> the
> >>structure of the already logical file, with the exception of one
> field
> >>and the logicals key sequence.  Is there another way to manipulate
> the
> >>existing logical (without having to build another logical)?
> >>I appreciate all responses
> >>:-Tim & Dana Truax-:
> >
> >
> >So why are you against another logical?  How many do you have over
> the
> >PF?  10?  50?
> >
> >If you need it build it.  Especially if it will be used by users
> using 
> >Query, SQL, etc.   Or use OPNQRYF or something.  How many records?
> Agreed.
> The AS/400 is very very good at amanging access paths; even over large
> files.  My prior employer's standard was to build a logical when
> needed
> for an interactive application, and to use OPNQRYF when needed for
> batch.
> I'm not sure if I'd follow that advice anymore, because the
> performance of
> the machine has become very, very good.
> Also, be aware that if you have multiple logical files with the same
> key
> structure, the /400 will share the access path, minimising the
> overhead
> involved in maintaining the access path...
> Buck Calabro
> Commsoft
        Also agree, except..
        The system can only share paths when the new logicals do not add
        That means if you have an existing logical L1 that is built over
        A and B. And you create logical L2 built over fields A, B and C,
        will not share access paths. To have them share, you need to
        L1, create L2, and then re-create L1.
        Similar restrictions apply to select/omit data and
        All that aside, if you need another path, build it. The burden
of maintaining
        a path versus having it when you need it is usually worth

        -Steve Cotes
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