SOURCE - http://www.geocities.com/srcsinc/drona/programming/languages/jcl/jcl.html
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.
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Upto 15 extends of secondary space ( in our example it is 4 ) will be alloted , If space is not sufficient. |
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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
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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 |
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~ by munchy on July 4, 2008.
Posted in JCL
Tags: DD statement JCL, JCL DD statement
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