InventDim and InventSum causes slow when browsing SO List Form

Hi there,

I have a scenario as below since last monday.

1. There is a heavy wait hours on this query
SELECT SUM(T1.POSTEDQTY),
   SUM(T1.POSTEDVALUE),
   SUM(T1.PHYSICALVALUE),
   SUM(T1.DEDUCTED),
   SUM(T1.RECEIVED),
   SUM(T1.RESERVPHYSICAL),
   SUM(T1.RESERVORDERED),
   SUM(T1.REGISTERED),
   SUM(T1.PICKED),
   SUM(T1.ONORDER),
   SUM(T1.ORDERED),
   SUM(T1.ARRIVED),
   SUM(T1.QUOTATIONRECEIPT),
   SUM(T1.QUOTATIONISSUE),
   SUM(T1.AVAILPHYSICAL),
   SUM(T1.AVAILORDERED),
   SUM(T1.PHYSICALINVENT),
   SUM(T1.POSTEDVALUESECCUR_RU),
   SUM(T1.PHYSICALVALUESECCUR_RU),
   SUM(T1.PDSCWPOSTEDQTY),
   SUM(T1.PDSCWDEDUCTED),
   SUM(T1.PDSCWRECEIVED),
   SUM(T1.PDSCWRESERVPHYSICAL),
   SUM(T1.PDSCWRESERVORDERED),
   SUM(T1.PDSCWREGISTERED),
   SUM(T1.PDSCWPICKED),
   SUM(T1.PDSCWONORDER),
   SUM(T1.PDSCWORDERED),
   SUM(T1.PDSCWARRIVED),
   SUM(T1.PDSCWQUOTATIONRECEIPT),
   SUM(T1.PDSCWQUOTATIONISSUE),
   SUM(T1.PDSCWAVAILPHYSICAL),
   SUM(T1.PDSCWAVAILORDERED),
   SUM(T1.PDSCWAVAILPHYSICAL),
   SUM(T1.PDSCWAVAILORDERED),
   SUM(T1.PDSCWPHYSICALINVENT)
FROM INVENTSUM T1
WHERE (((T1.PARTITION=5637144576)
AND (T1.DATAAREAID=N'123'))
AND ((T1.ITEMID=@P1)
AND (T1.CLOSED=@P2)))
AND EXISTS
   (
   SELECT 'x'
   FROM INVENTDIM T2
   WHERE (((T2.PARTITION=5637144576)
  AND (T2.DATAAREAID=N'123'))
  AND ((((T2.INVENTDIMID=T1.INVENTDIMID)
  AND (T2.INVENTSITEID=@P3))
  AND (T2.INVENTLOCATIONID=@P4))
  AND (T2.INVENTBATCHID=@P5)))
   )

2. The impact was on the SO module with following synptoms: -

a. Slow while browsing the SO list from All SO/Open SO
b. Add line still ok but when user confirm order, will hang for a while
c. changing view from line to header also will be slow

3. Upon investigation, what we did to improve the performance was to reindex Inventdim and Inventsum table from System admin--> SQL administration

4. After reindex, it works for a while. Performance back to normal.

5. However after overnight, in the morning, the issue came back and i need to do another round of reindex on these 2 tables.

6. Is it normal that i need to do reindex in a 12 hours period? I found this strange as we have never had this issue before.

Would appreciate someone can share some ideas.

Thanks,

Dave