Re: Index read performance

Also, noticed that the READE operation has taken same amount of time in all
3 tests, and that time was slightly less than the base SETLL time ( about
1.97 ms).

So that should rule out other system activity, I would think.

Maybe one of the SETLL took all the additional time due to some disc issue??


On Wed, Jan 27, 2016 at 6:52 PM, Vinay Gavankar <vinaygav@xxxxxxxxx> wrote:

The data was gathered using performance tool (i-doctor I think). With the
old file the elapsed time for SETLL operation (there is only one in the
program) took an average of 2 microsecs. With new file once it took 87 ms
and another time 197 ms.

The 3 tests were run on different days, I can't really comment on the
system load at each time. But between the second and third tests there was
no code change, so it SEEMS that this is related to other factors, but I am
not sure.

On Wed, Jan 27, 2016 at 12:40 PM, Charles Wilt <charles.wilt@xxxxxxxxx>
wrote:

Define substantial...are you looking at total wall-clock run time, CPU
usage or is the program instrumented so that you can see how long each
loop
takes?

I wouldn't expect a difference. How many time did you run it? Is it
possible that the first index was in memory? Use SETOBJACC POOL(*PURGE)
to
ensure that neither index is in memory between runs.

Are you sure workload on the system was comparable between runs?

Charles

On Wed, Jan 27, 2016 at 11:01 AM, Vinay Gavankar <vinaygav@xxxxxxxxx>
wrote:

Hi,

We have 2 indexes on a Table. First index is Key1, Key2 (Desc). Second
index is Key1, Key2 (desc), key3 (desc), key4 (desc).


Key1 is 18 char, key2 & key3 are 8 numeric and key4 is 6 numeric.

We had a program which was using the first index to read all records for
one value of Key 1 (Setll and Reade on Key1). That program was changed

to

use the second index (as they are planning to get rid of the first

index),

and a substantial performance degradation was observed.

Is this behavior to be expected due to the additional keys of the second
index?

The Table is huge and partitioned. There is no Implicit Access path

sharing

in either files.

Any suggestions to improve performance would be appreciated.
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