RE: Difference between Select and Omit in LF

[CWilt@xxxxxxxxxxxx]

Peter,

That's really interesting.....

I'm wondering if there's some problem in your testing procedure.  For
instance, do you always run the 'select' version before the 'omit' version.
Thus the omits gets to take advantage of the data already being in memory. 

I know I've seen some instructions before somewhere on how to do performance
comparisons.  Don't remember any specifics, but it did mention clearing out
memory pools between runs.

HTH,
Charles


> -----Original Message-----
> From: Peter Colpaert [mailto:Peter.Colpaert@xxxxxxxxxxxx]
> Sent: Wednesday, May 12, 2004 5:03 AM
> To: RPG400-L@xxxxxxxxxxxx
> Subject: Difference between Select and Omit in LF
> 
> 
> Hi group,
> 
> has anybody besides me noticed an enormous difference in 
> performance when 
> the following two logical files are read in the exact same 
> RPGLE program - 
> native SETLL and READ, no SQL:
> 
> A          R PSMAST                    PFILE(PSMAST)
> A* 
> A          K PSPACD 
> A          K PSCSNO 
> A          K PSCTNO 
> A* 
> A          S PSATFG                    COMP(EQ 'A') 
> A          S PSSTCD                    COMP(LT '30')
> 
> as opposed to
> 
> A          R PSMAST                    PFILE(PSMAST)
> A* 
> A          K PSPACD 
> A          K PSCSNO 
> A          K PSCTNO 
> A* 
> A          O PSATFG                    COMP(NE 'A') 
> A          O PSSTCD                    COMP(GE '30')
> 
> The 'omit' version seems about 10 times faster.  I haven't 
> actually timed 
> it, but the omit gives subsecond response, whereas the select 
> takes upto 5 
> seconds to retrieve approximately 35 records.
> 
> For what it's worth, the displayed data is of course 
> identical in both 
> versions of the file. I don't even need to recompile the 
> program when I 
> switch LF versions.
> 
> Is this performance difference normal, or am I missing something?
> 
> Thanks,
> 
> Peter Colpaert
> iSeries Application Developer
> 
> Honda Europe NV
> Langerbruggestraat 104
> B-9000 GENT
> Belgium
> Peter.Colpaert@xxxxxxxxxxxx
> Tel: +32 9 2501 334
> Fax: +32 9 2501 231
> ----------
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