IBM JCL Interview Questions and Answers

11/07/2009 No Comment

IBM JCL Technical Interview Questions and Answers.

What are the differences between JES2 & JES3 ?
Answer : JES3 allocates Data Sets for all the steps before the job is scheduled. In JES2, allocation of Data Sets Required by a step are done only just before the step executes. JOB /EXEC/DD ALL PARAMETERS JOBLIB/STEPLIB PROCEDURES, PARAMETERS PASSING CONDITION VARIABLES ABEND CODES.

What are the kinds of job control statements?
Answer : The JOB, EXEC and DD statement

What is the meaning of keyword in JCL?What is its opposite?

Answer : A keyword in a JCL statement may appear in different places and is recognized by its name, eg MSGCLASS in the JOB statement The opposite is positional words, where their meaning is based on their position in the statement, eg in the DISP keyword the =(NEW,CATLG,DELETE) meaning are based on first, second and third position.

Describe the JOB statement, its meaning, syntax and significant keywords.?

Answer : The JOB statement is the first in a JCL stream Its format is // jobname, keyword JOB, accounting information in brackets and keywords, MSGCLASS, MSGLEVEL, NOTIFIY, CLASS, etc .

Describe the EXEC statement, its meaning, syntax and keywords.?

Answer : The EXEC statement identifies the program to be executed via a PGM=program name keyword Its format is //jobname EXEC PGM=program name The PARM= keyword can be used to pass external values to the executing program.

Describe the DD statement, its meaning, syntax and keywords.?

Answer : The DD statement links the external Data Set name (DSN) to the DDNAME coded within the executing program It links the File names within the program code to the File names know to the MVS operating system The syntax is // ddname DD DSN=Data Set name Other keywords after DSN are DISP, DCB, SPACE, etc .

What is a PROC?What is the difference between an instream and a catalogued PROC?

Answer : PROC stands for procedure It is 'canned' JCL invoked by a PROC statement An instream PROC is presented within the JCL; a catalogued PROC is referenced from a proclib partitioned Data Set.

What is the difference between a symbolic and an override in executing a PROC?

Answer : A symbolic is a PROC placeholder; the value for the symbolic is supplied when the PROC is invoked, eg &symbol=value An override replaces the PROC's statement with another one; it substitutes for the entire statement

What is RESTART? How is it invoked?

Answer : A RESTART is a JOB statement keyword It is used to restart the job at a specified s step rather than at the beginning

What is a GDG? How is it referenced?How is it defined? What is a MODELDSCB?

Answer : GDG stands for generation data group It is a Data Set with versions that can be referenced absolutely or relatively It is defined by an IDCAMS define generation datagroup execution

Explain concatenating Data Sets ?

Answer : Data Sets can be grouped in a DD statement one after another, eg in a JOBLIB statement where the load module can exist in one of many Data Sets.

What is the difference between specifying DISP=OLD and DISP=SHR for a Data Set?

Answer : A DISP=OLD denotes exclusive control of the Data Set; DISP=SHR means there is no exclusivity .

What is MOD and when would you use it?

Answer : DISP=MOD is used when the Data Set can be extended, ie, you can add records at the end of an existing Data Set

What are the keywords associated with DCB? How can you specify DCB information? What is the OS precedence for obtaining that DCB information, ie where does the system look for it first?

Answer : The keywords associated with the DCB parameter are LRECL, RECFM, BLKSIZE and DSORG The DCB information can be supplied in the DD statement The system looks for DCB information in the program code first

How do you designate a comment in JCL?
Answer : The comment statement is //* followed by the comments.

What is the meaning of the EXEC statement keyword, COND? What is its syntax?

Answer : COND specifies the conditions for executing the subsequent job step The value after the COND= is compared to the return codes of the preceding steps and if the comparison is true, the step is bypassed (If this answer confuses you, welcome to the club - memorize it and don't ask questions!).

What is the improvement to COND= in the latest version of MVS?

Answer : MVS now allows for an IF bracketed by an END IF around any job step to replace the COND= syntax Again, if the IF statement is true, the step is bypassed.

What is the purpose of the PARM keyword in the EXEC statement?

Answer : The value after the PARM= specifies control information to be passed to the executing program of the job step

What is the purpose and meaning of the REGION keyword and what JCL statement is it associated with?

Answer : REGION specifies the maximum CPU memory allocated for a particular job or job step If REGION is in the JOB card, it relates to the entire job; if in the EXEC statement, it relates to the job step .

What is the purpose and meaning of the TIME keyword and what JCL statement is it associated with?

Answer : TIME specifies the maximum CPU time allocated for a particular job or job step If TIME is in the JOB card, it relates to the entire job; if in the EXEC statement, it relates to the job step.

What is the meaning of data definition name (DD name) and Data Set name (DSN name) in the DD statement?

Answer : Data definition name is the eight character designation after the // of the DD statement It matches the internal name specified in the steps executing program In COBOL that's the name specified after the ASSIGN in the SELECT ASSIGN statement Data Set name is the operating system (MVS) name for the File.

How is the keyword DUMMY used in JCL?

Answer : For an output File DUMMY specifies that the output is to be discarded For input it specifies that the File is empty.

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