REUSEDLT *NO and INSERTS

Question about a file with REUSEDLT *NO.  I figured this would be the best
REUSE setting for a file that receives large bulk inserts.  Essentially, we
end up deleting as much as 10% of the file and then INSERT a slew of updated
records as one batch.  I assumed this would place the records at the end of
the file - which would be easiest and quickest.  Howerver, when viewing the
QZDASOINIT job running the insert and selecting option 14 and then hitting
F11, there is a display for "Relative Record" - which I assume is the
current ordinal record position currently locked by the INSERT.

Well, the relative record number is jumping all over the place within the
file while I'm expecting to see an incrementally increasing relative record
number (previous maximum ordinal plus 1) since I'm expecting records to be
inserted at the end of the file.

Something else I was considering is maybe I am seeing the relative record
number of the unique index over the table - verifying the constraint before
each insert.  Maybe each insert is seeking on the unique constraint and I
just happen to see the ordinal position of the seek at the exact moment I
hit F11?

Anyway, can anyone add some color to the "relative record" display on the
Display Open File screen...as well as confirm that REUSEDLT *NO is the
fastest insert option.

Thanks

Ryan