I agree with the opinions expressed, but wish, as one writer has already, 
to stress the *reason*.

Thrashing the disk is a very bad idea.  If you want to do any operation 
whatsoever, on more than say thirty percent of any file, the best course is to 
do that operation in disk order i.e. frame order i.e. a straight SELECT or 
BASIC SELECT.

No form of index, sselect or any other order which is not the order in 
which the frames are laid down.

When you do the operations in order, the system will magically retain in 
memory the group on which you're working and possibly the next group as well 
(if it's using an optimistic look-ahead process) and whatever operations you 
do on that group will be very fast as they are being done in memory.

If you're jumping all over your disk, because you're selecting the items 
out of frame order, it will be quite slow.

W
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