DB qeury taking too long to execute

Hi,

This DB query is taking too long on the customer system!

DB stats checked with DB20. Everything seems okay!

Any Pointer which would lead me to solution are most welcome.

Query is:

"

SELECT DISTINCT * FROM /sapsll/cuhdsta

AS a

INNER JOIN /sapsll/cuhd

AS b

ON a_{mandt EQ b}mandt

AND a_{guid_pobj EQ b}guid_cuhd

INTO CORRESPONDING FIELDS OF TABLE lt_cuhd

WHERE a~prost IN lr_prost

AND a~sticm IN lr_sticm

AND a~pobjt EQ gc_pobjr-customs_doc_head.

"

The Table /sapsll/cuhdsta contains about 7 million entries.

Thanks,

Rohit.