>>>I can not see what causes your problem, but I have a few advices:
>>>1. Avoid SET FILTER whenever possible, instead you can use "BROWSE FOR yourcondition"
>>
>>BROWSE FOR is equal to SET FILTER. What are you referring to?
>
>Over the years I have had many problems when I used SET FILTER, so I stopped using it whenever I could. One problem was that it is easy to forget to reset it, and you end up with too few records. I don't remember the other problems, but since it's usually easier to add a FOR whatevercondition, I prefer that.
>
>>>2. Don't use GO TOP after SET FILTER, instead use LOCATE which in many cases is extremely much faster
>>
>>That's for sure!

It occurred to me there may be a performance benefit in this as well. It's not much, but...

USE members
LOCAL m.lnA, m.lnX
m.lnA = SECONDS()
FOR m.lnX = 1 TO 10000
SET FILTER TO UPPER(SURNAME)="Z"
SCAN
ENDSCAN
NEXT m.lnX
?SECONDS() - m.lnA

m.lnA = SECONDS()
FOR m.lnX = 1 TO 10000
SCAN FOR UPPER(SURNAME)="Z"
ENDSCAN
NEXT m.lnX
?SECONDS() - m.lnA

Gives me .349 seconds for the first block and .184 seconds for the second. No need for the LOCATE in the first as the SCAN does that.