See the section The OPEN Statement. 
            
            
               Additional Syntax Rules:
               
               
               
                  
                  - A report file must have sequential organization. 
 
                  
                  - The OPEN statement for a report file must contain only the OUTPUT phrase or the EXTEND phrase. 
 
                  
               
               
             
            
            
               Additional General Rules:
               
               
               
                  
                  - The OPEN statement for a report file must be executed prior to the execution of an INITIATE statement for any reports contained
                     in the file.