Help me with Points to be noted While creating a Secondary Index.

Question

Hi,
There is a Secondary index created on a Z table which already have 9 secondary indexes. This is the 10th index that is created.
The Index is created as follows
MANDT             Client
DOCNUM_REF     Document number
The Table data is huge and it is more than 4Lakh records.
I have done the following analyses.
1) The fields to be used are not in any other indexes.
2) The Data is mostly different, i.e. The document reference field is having distinct data
  select a~docnum a~werks_o a~docnum_ref a~natop
         a~m_icms a~m_ipi
         b~lgort_out b~mov_est
         b~item b~matnr
    appending table ti_requisicoes
    from zsytmm_reqnfcb as a
   inner join zsytmm_reqnfit as b
      on a~branch_o eq b~branch_o
     and a~requi    eq b~requi
     and a~mask     eq b~mask
     for all entries in ti_doc_saida_del
   where a~docnum_ref   eq ti_doc_saida_del-docnum.
What else I need to check , so that the index improves the performance. The table is using in 300 reports.

Answer 1

Ravishankar Lanjewar wrote:
@SAP LEARNER,
>
> There is a Secondary index created on a Z table which already have 9 secondary
> indexes. This is the 10th index that is created.
>
>
> I will not recommand to create index any more on this table. If you want to create secondary index for on above table which you have mention. You don't create index only for hamper of performance of single program/report.
>
> Don't create more than 4 to 5 index on sinlge table.
>
> Refere the tread Link:[Why to create Secondary index ?|Re: When is a secondary index used (in select or where)]
Sounds like another myth that is widely spread across SAP community.
Remember, complex systems like modern DBMS do not like generalizations. I personally know standard SAP tables with 9 standard secondary indexes. In the meantime the hardware became fast enough to update several secondary indexes without really significant problems. Of course indexes require space, of course one should create indexes that are not similar and differ from each other with more than one field for example. In other words, think before creating!
But it's again incorrect to say "do not create because you already have 9 others". You did not even ask what fields are in the affected table, what are the existing indexes.
Ravishankar Lanjewar wrote:
> I will recommand to delete all the index and create 4 to 5 fresh index while doing analysis for all SQL statement using where use list  depends on where condition of SQL.
I am now trying to imagine the effort to analyze 300 reports using this table and all corresponding selects. And probably you will drop supporting indexes for several reports. Some of them may be CEO/CFO-relevant reports that will run minutes/hours instead of seconds. And I would like to see the reaction of CEO when he finds out that it was the result of your "optimization" activities.