Performance issue in CDHDR & CDPOS

Question

Hi,
  I'm having the below QUERY on CDHDR which take a <bowdlerized> lot of time:
SELECT OBJECTCLAS
         OBJECTID
         CHANGENR
         TCODE
         UDATE
         UTIME
    INTO TABLE IT_CDHDR2
    FROM CDHDR
   WHERE OBJECTCLAS = C_OBJECT
     AND OBJECTID   = C_OBJECT
     AND ( TCODE    = C_TCODE1 OR                    
           TCODE    = C_TCODE2 ). 
Then I've the other select query on CDPOS using for all entries on IT_CDHDR2. Both the queries are taking a lot of time.in the CDPOS select query I'm passing all the keys in order while I couldn't do that  for CDHDR. Kindly advise if anyone has worked on the performance issues with CDHDR/CDPOS. What are all the possible ways of improving the performance of CDHDR / CDPOS.
Thanks:
Gaurav
Edited by: Rob Burbank on Jun 10, 2011 3:00 PM

Answer 1

Hello Gaurav,
basically John was right.
Table CDHDR has first key fields MANDT, OBJECTCLAS, OBJECTID.
Object ID is normally selective enough to provide good performance for the select that you mentioned.
The only reason that comes to my mind is the outdated statistics.
When the database decides whether to make an index scan or a full table scan, it looks at the table statistics (number of rows, selectivity, etc.).  Tables like CDHDR grow after GoLive of the system. If the statistics was last collected when this table was small, the database will think that it will be cheaper to do a full table scan. And it is not the case anymore.
Please go to the transaction DB20 and update statistics for CDHDR and CDPOS tables.
See if it helps.
Regards,
  Yuri