Re: what say you about subfiles?

[Vernon Hamberg <hambergv@xxxxxxxxxxxxxx>]

Booth

At 08:34 PM 5/26/1998 -0400, you wrote:
>I just was looking over IBM's sample subfile program in VaRPG.  I'd
>copied, it, changed the file to display a data file on our AS/400 and was
>showing the output to someone that knows the data.  The VaRPG subfile
>offers a "navigator bar", and one of the icons is "Last page."  He clicked
>it and laughed, saying "This is a 40,000 record file. Lets see..."  and
>then looked really funny.  Then he looked again and said "It can't read
>the file that fast!"   
>
>To make a boring story short, a review of the code showed that the last
>page had been loaded by taking the number of records in the file and
>subtracting the page size, and filling the subfile from that point.  Very
>neat, very fast.  Also a new technique I'd not seen before.
>
>All of which puts me of a mind to ask for a religious discussion on
>subfiles.  If DOU and DOW can start lengthy debate, I should think proper
>subfile techniques could be fascinating.  
>
>One of the downsides of the technique described is that it appears to work
>on a physical file only, disregarding all logicals, even if specified.

Interesting idea. But it would not be reliable, IMO, even on physicals
because of skipped RRNs.

A possible alternative would be to position at EOF and READP the number of
records = to page size. Maybe? This should also work on logicals.

Cheers

Vernon Hamberg
Systems Software Programmer
Old Republic National Title Insurance Company
400 Second Avenue South
Minneapolis, MN  55401-2499
(612) 371-1111 x480


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