Select query performance improvement - Index on EDIDC table

Question

Hi Experts,
I have a scenario where in I have to select data from the table EDIDC. The select query being used is given below.
  SELECT  docnum
          direct
          mestyp
          mescod
          rcvprn
          sndprn
          upddat
          updtim
  INTO CORRESPONDING FIELDS OF TABLE t_edidc
  FROM edidc
  FOR ALL ENTRIES IN t_error_idoc
  WHERE
  upddat GE gv_date1 AND
  upddat LE gv_date2 AND
  updtim GE p_time AND
  status EQ t_error_idoc-status.
As the volume of the data is very high, our client requested to put up some index or use an existing one to improve the performance of the data selection query.
Question:
4.    How do we identify the index to be used.
5.    On which fields should the indexing be done to improve the performance (if available indexes donu2019t cater to our case).
6.    What will be the impact on the table performance if we create a new index.
Regards ,
Raghav

Answer 1

Question:
1.    How do we identify the index to be used.
Generally the index is automatically selected by SAP (DB Optimizer )  ( You can still mention the index name in your select query by changing the syntax)
  For your select Query the second Index will be called automatically by the Optimizer, ( Because  the select query has u2018Updatu2019 , u2018uptimu2019 in the sequence before the u2018statusu2019 ) .
2.    On which fields should the indexing be done to improve the performance (if available indexes donu2019t cater to our case).
(Create a new Index with MANDT and the 4 fields which are in the where clause in sequence  )
3.    What will be the impact on the table performance if we create a new index.
( Since the index which will be newly created is only the 4th index for the table, there shouldnu2019t be any side affects)
After creation of index , Check the change in performance of the current program and also some other programs which are having the select queries on EDIDC ( Various types of where clauses preferably ) to verify that the newly created index is not having the negative impact on the performance. Additionally, if possible , check if you can avoid  into corresponding fields .
Regards ,
Seth