Friday, 8 July 2011
JOB CONTROL LANGUAGE (JCL)
Brief Introduction
what is JCL?
Job control language. It is a means of communication between a program that can be written in COBOL , ASSEMBER or PL/I and the MVS operating system. Without a JCL, you cant able to run a job on MVS operating system. Let us start with an example jcl, how it looks like, The following jcl is used to run an cobol program. I will explain in this blog each and every line of this jcl.
JCL , used to run a cobol program //JOB1 JOB (024),'NEERAJ BHATT',CLASS='A',PRTY=6 //STEP01 EXEC PGM=COBPROG. //INFILE DD DSN=SED.GLOB.DES.INFILE,DISP=SHR //OUTIFLE DD DSN=SED.GLOB.DES.OUTFILE, // DISP=(NEW,CATLG,DELETE), // UNIT=DISK, // SPACE=(CYL,(1,5),RLSE), // DCB=(RECFM=FB,LERECL=70,BLKSIZE=700)
All JCL statements can consists of up to five types of fields // The two forward slashes are required at the beginning of each JCL statement in Columns 1 and 2. Name field - This is an optional field. If coded, should start at Column 3. It maximum length is 8. Operation field - Which indicates the operation that is to be performed Operand - This field must appear after Operation field. Must start at 16 column Comments - Comments begin one space after the last operand. Our simple example has no comments.
The three important input operations are 1. JOB 2. EXEC 3. DD Now first look at JOB statement Syntax of JOB Statement
Now i will explain you the keyword parameters one by one :- (CLASS PRTY MSGCLASS MSGLEVEL TYPRUN NOTIFY) 1. CLASS - Some jobs can be short running, some jobs may take more time other may use heavy resources. CLASS keyword parameter is used to tell to OS about the nature of job we are submitting. Syntax -> CLASS=jobclass Valid values -> Any alphabetical character between A - Z or numbers between 0 - 9 Example JCL -> //MYJOB JOB (024),'NEERAJ',CLASS=K 2. PRTY - It is related to CLASS parameter. It assigns priority to jobs which belong to the same class. Higher number takes precedence over the job with lower number. A job with priority of 12 will run before a job with priority 5. Syntax -> PRTY=priority Valid values -> Any value between 0 to 15 Example JCL -> //MYJOB JOB (024),'NEERAJ',CLASS=8,PRTY=6 3. MSGCLASS - The MSGCLASS parameter determines the output device to which system messages and JCL messages are written Syntax -> MSGCLASS=output-class-name Valid values -> Any alpha betical character between A - Z or number between 0 - 9 Example JCL -> //MYJOB JOB (024),'NEERAJ',CLASS=7,PRTY=5,MSGCLASS=A 4. MSGLEVEL - is used to tell JCL, which messages to be printed in the device specified in MSGCLASS parameter Syntax -> MSGLEVEL=(statements,messages) Valid values -> Statements may be the number 0,1,2 and messages can be 0 or 1 STATEMENT 0 - Related to job statements only printed 1 - Jcl will be printed (which includes all cataloged/symbolic parameters) 2 - only the input jcl statements being printed MESSAGES 0 - Allocation/termination messages will be printed If job terminates abnormally 1 - Allocation/termination messages will be printed regardless of whether the job terminates normally or abnormally. Example JCL -> //MYJOB JOB (024),'NEERAJ',CLASS=8,MSGCLASS=S,MSGLEVEL=(1,1) 5. TYPRUN - The TYPRUN parameter is used to specify whether job is to be held until further notice or for syntax checking Syntax -> TYPRUN=HOLD - Job held until further notice
or
TYPRUN=SCAN - Check Jcl for syntax checking
Example JCL -> //MYJOB JOB (024),'NEERAJ',CLASS=8,PRTY=9,TYPRUN=HOLD
6. NOTIFY - The NOTIFY parameter is used to direct the system, where it has to
send the success/failure message after completing the job.
Syntax -> NOTIFY=userid/&SYSUID
EXAMPLE JCL -> //MYJOB JOB (024),'NEERAJ',CLASS=8,NOTIFY=&SYSUID
&SYSUID - the userid from which user it has been submited
//MYJOB JOB (024),'NEERAJ',CLASS=8,NOTIFY=BRM46
It send the sucess/failture message to BRM46 useridJOBLIB / STEPLIBJOBLIB It is a DD (Data definition) statement, and it specifies where the program (which is specified in EXEC statement) exists. It is applicable to all job steps in that job. It cannot be used in cataloged procedures. Syntax -> //JOBLIB DD DSN=dataset EXAMPLE JCL -> //MYJOB JOB (024),'NEERAJ' //JOBLIB DD DSN=SE.TEST.LOADLIB,DISP=SHR <--- NOTE //STEP1 EXEC PGM=COBPROG Immediately following the JOB statement is the JOBLIB DD statement. This is used to specify the location of the program that is to be executed. STEPLIB It is also like JOBLIB. It is used to tell in which dataset program resides, It will be coded in JOB STEP. It is only for that step instead of entire JOB. It can be placed any where in the job step. STEPLIB can be coded in cataloged procedures. Syntax -> //STEPLIB DD DSN=dataset Example JCL -> //MYJOB JOB (024),'NEERAJ' //STEP1 EXEC PGM=COBPROG //STEPLIB DD DSN=TEST.MYPROD.LIB,DISP=SHR //STEP2 EXEC PGM=COBPROG2 //STEPLIB DD DSN=TEST.MYPROD.LIB1,DISP=SHR
IIn above example, STEP1 is executing COBPROG which is member of TEST.MYPROD.LIB STEP2 is executing COBPROG2 which is member of TEST.MYPROD.LIB1
EXEC STATEMENT EXEC statement is used to execute a program/procedure
A maximum of 255 EXEC statement can code in an single job
Syntax - //stepname EXEC PGM=program-name,keyword parameters
Positional parameter - Program-name
Keyword parameters for EXEC
PARM ACCT ADDRSPC DPRTY PERFORM RD
PARM
PARAM parameter is used to pass information to program
Syntax -> PARM=value
Value is a string can be 1 to 100 characters long.
PASSING PARAMETER USING PARM PARAMETER ACCT - accounting information for that step ADDRSPC - used to indicate to the system that the job step is use either virtual or real storage DPRTY - used to assign priority to the job step PERFORM - specifies the rate at which system resources used by job step RD - restart definition is used to specify automatic restart of a job if it abends
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