EVAL strange behavior... (Barbara con you explain it)

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Today I've tested a pgm that order an OCCUR DS trought an array and I see that 
the pgm have a strange behavior on a EVAL instructioin.
The pgm work are like that:


D SKCRER          S                   DIM(500) LIKE(CRER)

D CRER            DS                  OCCURS(500) INZ
D  REX                    1      6
D  REC                    7    114P 3
D                                     DIM(12)
D                                     PACKEVEN
D  REP                  115    222P 3
D                                     DIM(12)
D                                     PACKEVEN


C     ORDCRER       BEGSR
C*
C                   CLEAR                   SKCRER
C*
C* PASSO L'OCCUR NELLA SCHIERA
C     1             DO        500           YY
C     YY            OCCUR     CRER
C                   EVAL      SKCRER(YY) = CRER                         <====
C                   ENDDO
C*
C* ORDINO LA SCHIERA
C                   SORTA     SKCRER
C*
C* PASSO LA SCHIERA NELL'OCCUR
C     1             DO        500           YY
C     YY            OCCUR     CRER
C                   EVAL      CRER = SKCRER(YY)
C                   ENDDO
C*
C                   ENDSR


If I replace the C spec "<====" with the follow spec all works fine!!!

C                   MOVEL     CRER          SKCRER(YY)                  <====

Has someone any ideas???

Thanks a lot



Fabrizio Gurrieri - BARTOLINI SPA
Via E.Mattei  42 - 40138 BOLOGNA (Italy)
Tel:+39 051 6015593 - Fax:+39 051 530365
E-Mail: Fabrizio.Gurrieri@bartolini.it
Internet: http://www.bartolini.it <http://www.bartolini.it/>