SQL index selection relies heavily on the precision of ESTKEY() to pick the best index. Prior behavior was for ESTKEY() to return the estimate to within 1/10 percent. New behavior increases the ESTKEY() precision with the number of keys in the file to attempt to maintain a precision of about 100 records. As this is done using a binary search on the high and low keys, it requires 2 additional index searches for each doubling of the file size. This option reverts to the prior behavior.