...................................
          OPEN (BLOCK,(INPUT))                                           
          C     15,=F'0'                                                 
          BE    OPEN                                                     
          C     15,=F'8'                                                 
          BNE   OPENERR                                                  
          ST    15,SAV15                                                 
          SHOWCB ACB=BLOCK,FIELDS=ERROR,AREA=ACBERFLG,LENGTH=4,AM=VTAM   
          C     15,=F'0'                                                 
          BNE SHOWERR                                                    
          L     5,ACBERFLG    reason code 1 byte right justified         
          L     15,SAV15                                                 
          C     5,=F'160'     reason 160 VSAM is not initialized         
          BNE   OPENERR                                                  
          WTO   TEXT=NOTINIT                                             
          B     ENDPGM                                                   
 SHOWERR  EQU *                                                          
          LR    10,15                                                    
          ABEND 110,REASON=(10)                                          
 OPENERR  EQU *                                                          
          LR    10,15                                                    
          ABEND 111,REASON=(10)   reason is different than 160           
 OPEN     EQU   *                                                        
...................................