Multiple occurance data structure

I have kind of an odd problem - an RPG III program
uses a multiple occurance data structure defined
for 25 occurances like so:

IMDEARN DS      25
I               1       4 NONTAX

The structure is filled with some number of values
from a database file, then later traversed in a DO
loop.  The loop exit criteria is that a field from
the DS = *blanks, e.g. no value loaded from the
file, e.g. "End Of File" (yeah it's bad technique - I
didn't write it, it's legacy code!), like so:

C                         Z-ADD   1           INDX      
C       INDX            OCUR    MDEARN
C       NONTAX  DOWNE*BLANKS
                  <process DS entry>
C                        ADD  1       INDX
C       INDX             OCUR    MDEARN
C                        END

Problem - program blows up on an "index out of
range error" for one of our client's whose
database has 10 values to be loaded into MDEARN,
e.g. the error occurs when INDX in the above
snippet reaches 11.  I'm confused... since MDEARN
is defined w/25 occurances, 11 shouldn't cause an
index error, right?  Compile listing shows
MDEARN(25) and yet, sure enough, in the program
dump after the error, MDEARN says dimension(10)
and only shows 10 spaces allocated to the
structure.  What's up with this... did RPG III
suddenly start allocating memory for data
structures dynamically?

TIA

Scott Cornell, Mercy Information Systems
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