rolbk causing reade to read the same record

I'm encountering a strange problem.  I'm seeing my reade reading the
same record when rolbk is executed.  Is this normal for rolbk to cause
this reade behavior?  
 
Below is a sample code and program will go into infinite loop (reade
reading the same record over and over again).
 
DDS for MYFILE:
  R MYFILEFMT       
    MYFILEKEY      3
    MYFILEDATA     3
  K MYFILEKEY       

 
Added the following two records to MYFILE and run the program below
XXX   AAA
XXX    BBB
 
 
RPG program:
FMYFILE    UF   E           K DISK    commit   
                                               
C                   eval      MYFileKey = 'XXX'
C     MYFileKey     setll     MYFILE           
C     MYFilekey     reade(e)  MYFILE           
C                   dow       not %eof         
C                   if        'a' = 'b'        
c                   update    MYFILEfmt        
C                   endif                      
C                   rolbk                      
C     MYFileKey     reade(e)  MYFILE           
C                   enddo                      
                                               
C                   eval      *inlr = *on