Special DD Statements

CHAPTER - 7 Special DD Statements

1.  DUMMY 
    DSN=NULLFILE

2.  Concatenating Data sets

3.  Passing data to cobol program  using -  SYSIN DD * 

4.  SYSOUT

5.  SYSUDUMP

6.  SYSADUMP



 1. DUMMY or DSN=NULLFILE

      Some times we need to testing of program, without using actual datasets. 

      Then we can use DUMMY or DSN=NULLFILE.

      If we use DUMMY, operating system simulates the presence of a file. When 
      you reading Operating system sends end of file request to program.

       Example JCL  -->   //MYJOB   JOB   (W345),'KRISHNA REDDY'
                          //STEP1   EXEC  PGM=COBPROG
                          //INFILE  DD    DUMMY



2. CONCATENATING DATA SETS 

      In JCL , we can concatenate different files by giving their name one after
   another. All data sets concated must be of the same type. For example, 
   partitioned data sets can be concatenated only with partitioned data sets.

      Example JCL  -->   //MYJOB   JOB   (W345),'KRISHNA REDDY'
                         //STEP1   EXEC  PGM=COBPROG
                         //INFILE  DD    DSN=TEST.GLOB.FILE1
                         //              DSN=TEST.GLOB.FILE2
                         //              DSN=TEST.GLOB.FILE3
 
      In program , we will read it as an single file. concatination of three 
      files done by operating system.

3. PASS DATA TO COBOL PROGRAM USING - SYSIN DD *                           

       This is the one of the way of passing data to program. There are two 
       syntax's to pass data.

                  Syntax1  ->  //MYJOB   JOB   (W234),'RAMESH'
                               //STEP1   EXEC  PGM=COBPROG
                               //SYSIN   DD    *
                                 
                               /*

                  Syntax2  ->  //MYJOB   JOB   (E345),'KRISHNA REDDY'
                               //STEP1   EXEC  PGM=COBPROG
                               //SYSIN   DD    DATA
                                 
                               /* 

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4. SYSOUT 

       The SYSOUT parameter is used to send the output which is generated during 
       job execution.

     Syntax      ->  //ddname  DD  SYSOUT=class

                 EXAMPLE JCL ->  //MYJOB  JOB  (R456),'KRISHNA REDDY'
                                 //STEP1  EXEC PGM=COBPROG
                                 //INFILE DD   SYSOUT=A

                 In this example, COBPROG is executed and all generated outputs 
                 are directed to class ( here it is letter A) 


5. SYSUDUMP   

      SYSUDUMP is used to dump the content of various registers, variables and 
      datasets acccessed at the time of abnormal termination, into a dataset.  
      The dump is in hexadecimal.
                  

                  Syntax  -->   //SYSUDUMP  DD   .....

                  EXAMPLE JCL -->   //MYJOB     JOB   (W345),'RAMESH'
                                    //STEP1     EXEC  PGM=COBPROG
                                    //SYSUDUMP  DD    DSN=TEST.PROD.LIB
              



6. SYSABEND

      SYSABEND is used to dump the contents of various registers variables , 
      datasets accessed and The nucleus at the time of abnormal termination.
      The dump is in hexadecimal.

                  Syntax  -->  //SYSABEND  DD  .....

                  EXAMPLE JCL -->  //MYJOB    JOB   (WE345),'KRISHNA REDDY'
                                   //STEP1    EXEC  PGM=COBPROG

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