S/O for file I/O? Yes, and also for optimization. Now that the default
for the QAQQINI setting, IGNORE_DERIVED_INDEX, is *NO, S/O LFs are
available to the optimizer.
This is basically the same as the sparse index - which has a WHERE
clause - and we can also specify the columns to be presented by the
INDEX - so this becomes almost exactly the same as an S/O logical.
We have been able to use indexes in RPG in F-specs - the newer kind of
index is just as useful for I/O as S/O logicals, and also for
optimization of SELECT statements that include a matching element in the
WHERE clause or probably in a JOIN.
On 5/1/2014 1:51 PM, Alan Campin wrote:
If you are using SQL, use the physical and let SQL tell you what indexes to
use with the Index Advisor. Select/Omit logicals is for file I/O
On Thu, May 1, 2014 at 12:20 PM, Vicki Wilson <VWilson@xxxxxxxxxxxxx> wrote:
I'm new at a company that has launched a DDS to DDL initiative.
The idea has been introduced to replace our select/omit logicals with
The idea of a sparse index is new to me and I'm wondering about best
practices regarding sparse indexes.
The first thought that comes to mind is that I was always taught not to
use select/omit logicals. Quite frankly this has been so ingrained in me
that I'm not sure why anymore. The most obvious argument is that when
researching code it's frustrating. Some of the business logic is hidden in
the logical and being new to the environment I don't always realize what
might be happening outside of the program.
For that reason alone I'm not a fan of creating sparse indexes to replace
select/omit logicals. For review/analysis purposes - it would hide some of
the business logic.
But the idea of a sparse index also perplexes me for another reason. I
thought the idea in SQL was always to reference the table - not a logical.
And let the engine do the work. If you used sparse indexes wouldn't you
have to reference the specific index?
Thoughts on best practices and references would be appreciated. I tried a
google search and did not come up with much.
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