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DRONA SERIES
JCL STUDY MATERIAL


CHAPTER - 6



   
 

DD STATEMENT

The DD statement (Data Definition), is used to identify the source of input 
and the placement of output information


Syntax  ->  //ddname  DD  < positional / keyword parameters >

            ddname must be unique in the job

      
            Positional parameters -  *
                                     DATA
                                     DUMMY
                                     DYNAM

            Keyword Parameters   -   DSN
                                     DISP
                                     UNIT
                                     SPACE
                                     DCB
                                     VOLUME   

DSN PARAMETER 

    DSN parameter is used specify the data set name

    Syntax  ->  DSN=dataset name

    Example JCL ->  //MYJOB   JOB   (ER3),'RAMESH R' 
                    //STEP1   EXEC  PGM=COBPROG
                    //INFILE  DD    DSN=TEST.GLOB.MYLIB
 
                    TEST.GLOB.MYLIB will be used in the COBPROG program.



TEMPORARY DATA SETS
  
    Temporary data set is created during job and deleted at the end of the job.  

    Temporary data set can be coded by using two ampersands followed by name.

    Example JCL  --> //MYJOB   JOB   (E456),'RAMESH'
                     //STEP1   EXEC  PGM=COBPROG
                     //INFILE  DD    DSN=&&TEMP         

    Here TEMP is an temporary dataset will be deleted upon job completion.




DISP PARAMETER

   The DISP parameter is used specify the disposition of dataset which is
   coded on DSN parameter. 

   Syntax   ->      

                    

         

   Parameter on the DISP statement


         Status                   Normal Disposition           Abnormal Disposition


         NEW                      DELETE                       DELETE 
         OLD                      CATLG                        CATLG  
         MOD                      UNCATLG                      KEEP
         SHR                      KEEP                         UNCATLG
                                  PASS 

        

    STATUS  

          NEW  -  Dataset will be created. (file should not exists)
          OLD  -  Dataset should exists.
          MOD  -  Dataset will be created If not exists.
          SHR  -  Dataset can be used by other jobs also



    NORMAL DISPOSITION   
    (Happened upon sucessful execution of job step)

          DELETE  -  Dataset should be deleted
          CATLG   -  Dataset will be cataloged
          UNCATLG -  Dataset will be removed from system catalogs
          KEEP    -  Dataset will be retained (This parameter should 
                     be used with permanent data sets)
          PASS    -  Dataset is to be passed subsequent job step in 
                     the same job



    ABNORMAL DISPOSITION 
    (Happened upon unsucessful execution of job step)

          DELETE  -  Dataset should be deleted
          CATLG   -  Dataset will be cataloged
          UNCATLG -  Dataset will be removed from system catalogs
          KEEP    -  Dataset is to be kept



    EXAMPLE JCL -->   //MYJOB   JOB   (E674),'KRISHNA REDDY'
                      //STEP1   EXEC  PGM=COBPROG
                      //INFILE  DD    DSN=TEST.GLOB.TEMP,
                      //              DISP=(NEW,CATLG,DELETE)


    In this example , 
		                
          DISP=(NEW,CATLG,DELETE)

          NEW    - TEST.GLOB.TEMP is not exists, it will be created

          CATLG  - Upon successful execution of job step, data set 
                    will be cataloged

          DELETE - If job terminicated abnormally, dataset will be deleted
        




UNIT PARAMETER


    In IBM Mainframe environment, All devices have an address assigned to 
    them at the time they added to the sytem. Devices can be referenced 
    using this addresses. UNIT parameter is used to specify thise address.

    Syntax  ->   UNIT=device_address/device_type/device_group_name/TAPE

        
    EXAMPLE JCL -> //MYJOB  JOB   (R345),'KRISHNA REDDY'
                   //STEP1  EXEC  PGM=COBPROG
                   //INFILE DD    DSN=TEST.GLOB.TEST.LIB,
                   //             UNIT=SYSDA

    In above example, COBPROG is executed, and a file INFILE  which may 
    reside on any of the devices  which are grouped under the symbolic name 
    SYSDA will be accessed




VOL PARAMETER


    This parameter is used to identify the volume serial number on which 
    dataset is reside. The VOL dataset is used with disk and tape datasets.


    Syntax  ->   VOL= volumelabel/data set label  


    Sub parameters used with VOL parameter

        SER     -  Specification of serial number
        REF     -  Referencing VOL specification from a prior step
        PRIVATE -  Allowing access to volume by single user
        RETAIN  -  Inhibiting dismounting of volume until end of job
        SEQ     -  Specification of sequence in which volumes are to be mounted


    EXAMPLE JCL -->  //MYJOB   JOB   (E454),'KRISHNA REDDY'
                     //STEP1   EXEC  PGM=COBPROG
                     //INFILE  DD    DSN=TEST.GLOB.TEMP,
                     //              VOL=SER=(VOL1,VOL2,VOL3)

    In this example the data set called DATA3 resides on 3 volumes whose 
    serial numbers are VOL1,VOL2,VOL3. The Operating system will request 
    that all volumes be mounted at the same time.







SPACE PARAMETER The SPACE parameter is used to allocate space for datasets. We can allocate space in Cylinders/Tracks/Blocks Syntax -> SPACE=(CYL,(primary,secondary,directory),RLSE,CONTIG,MXIG,ROUND) Instead of CYL, We can use TRK or BLK Meaning of Sub Parameter TRK - Requesting space in track CYL - Requesting space in cylinders PRIMARY - Primary storage to be allocated at the time of data set created SECONDARY - Additional storage to be allocated , If primary storage is not sufficient DIRECTORY - Space for recording of name and location of partitioned data sets RLSE - Request for release of space previously allocated unused space after completion of job CONTIG - Request for contiguous space MXIG - Request for large aread of contiguous space ROUND - Request for entire cylinder for storage of data set EXAMPLE JCL -> //MYJOB JOB (W345),'KRISHNA REDDY' //STEP1 EXEC PGM=COBPROG //INFILE DD DSN=TEST.GLOB.LIB // UNIT=4560 // SPACE=(CYL,(30,4)) In this example, 30 cylinders are requested as primary space and 4 additional cyliders as secondary space.
Upto 15 extends of secondary space ( in our example it is 4 ) will be alloted , If space is not sufficient.
DCB PARAMETER Records in dataset may contain FIXED length / VARIABLE length. The DCB (Data Control Block) parameter is used to specify record format,record length, block size etc.. Syntax -> //ddname DD DCB=< parameters > Subparameters in DCB RECFM - Specification of record format - F/FB/V/VB/U LRECL - Specification of record length BLKSIZE - Specification of block size BUFNO - Specification of buffers EXAMPLE JCL -> //MYJCL JOB (E3445),'RAMESH' //STEP1 EXEC PROG=COBPROG //INFILE DD DSN=TEST.GLOB.LIB // UNIT=234, // DSN=(LRECL=80, // RECFM=FB, // BLKSIZE=800, // BUFNO=30) In this example, The DCB parameter specifies that this file is to have a logical record length of 80 bytes, it will have a fixed block record format, and the block will 800 (800 is multiple of 80). The BUFNO parameter is set to 30, indicating upto 30 buffers may be utilized in virtual storage for this data set. Default buffers are 5,if you not specified any thing
When you specified V for RECFM parameter, LRECL value is largest record in the file plus 4 bytes. These four bytes contain the actual length of each variable length record in the file
    

NEXT CHAPTER TOPIC : SPECIAL DD STATEMENTS



                                   



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