we have weekly refresh of our db, right after refresh, we find one function in application is hanging, then we find out the script of that function. we decide to add an index to one table which is main part of that involved script, then the problem went away. After the problem gone, even we drop that index, we will not have any problem untill next week after the refresh, the same problem come back again. then we will do the same, add index, then drop. Any one has any idea? It looks like that it does not matter if sql use the added index, but put the table into memory by adding the index that really matters? Thanks.