Effect of Secondary Index on Performance Tuning

Question

Hi,
I have a select statement with the below where statement.
WHERE keyz1 = IT_dfkkzk-keyz1
AND bldat IN s_pblda
AND valut IN s_pvalu.
Table from data is accessed Primary key is a combination of two fields KEYZ1 & POSZA.
We have a Secondary Index with OPBEL & KEYZ1.
Will Optimizer will use Secondary Index?
If we change the where statement as given Below
WHERE keyz1 = IT_dfkkzk-keyz1
Will the access be fast?
Should i create a secondary index on keyz1 to make it fast?
Thanks & Reagrds
Lijo Joseph

Answer 1

Hi Lijo Joseph,
I think, optimizer will use primary key because "WHERE keyz1" references the first part of this key. Even if you change your WHERE-statement as considered, this will not change optimizer approach.
And yes, this access should be the fastest way to access you data, besides you have more values to reduce the amount of resulting rows. For example if you could specifiy POSZA too, this would accelerate access.
Creation of another secondary index on keyz1 will not make it faster, maybe if you include bldat and valut in this key. But notice, insertion and modification of data will then be slower.
To get optimizer to use existing secondary index you have to specify OPBEL in your where condition like this:
"where OPBEL = 'X' and KEYZ1 = ....."
Herbert