JCL questions on JOB, EXEC, AND PARM.
What is the purpose of the JOB statement?Answer : The purpose of the JOB statement is to inform the operating system of the start of a job, give necessary accounting information and supply run parameters. Each job must begin with a single JOB statement.
How does one identify a job to the Operating system?
Answer : A job is identified to the system by the use of jobname. Jobnames can range from one to eight alphabetic characters. The first character must begin in column 3 and be alphabetic (A-Z). Jobs should be given unique names since duplicate jobnames will not execute until any job having the same jobname completes execution.
What does the accounting information consist of?
Answer : Accounting information consists of the account number of which the job is charged and any additional information established by the installation.
What does the parameter CLASS in the JOB statement mean?
Answer : Parameter CLASS specifies the job class. There are 36 possible job classes (A-Z, 0-9). Installations usually attempt to establish job classes that achieve a balance between I/O bound and CPU-bound jobs. Job classes also determine the overall priority of a job, along with the PRTY parameter PRTY may be coded to give special priority to a job. The operator may also set it.
What is parameter MSGCLASS in the JOB statement used for?
Answer : The MSGCLASS parameter is used to specify the job scheduler message output class. The output classis (A-Z,0-9). Job scheduler message include all messages not printed by the actual job steps being executed. Some of these are: JCL statements and error messages, device allocations, dataset disposition and accounting information.
What does parameter MSGLEVEL on the JOB statement mean and what is the advantage of using it.
Answer : MSGLEVEL indicates whether or not one wishes to print the JCL statements and allocation messages. The MSGLEVEL parameter can save paper. After a job is debugged, there may be no need to print all the JCL and allocation messages each time it runs. To reduce printing to a minimum one may wish to code MSGLEVEL = (0,0)
which parameter allows one to run a syntax check n the JCL without executing it?
Answer : TYPRUN = SCAN parameter is used to check the JCL for syntax errors and suppress the execution of the job. This checking does not include checking for duplicate datasets on volumes, insufficient space or region size for job steps.
What does parameter TYPRUN = HOLD mean?
Answer : The parameter TYPRUN = HOLD holds a job in the input queue for later execution. The job is held until the operator releases it. TYPRUN=HOLD is useful for when one job must not run until another job completes. Operator intervention is required to release the job.
What is the purpose of the EXEC statement?
Answer : The purpose of the EXEC statement is to name a program or procedure to be executed. It follows the job statement. A job or cataloged procedure can contain several EXEC statements. A job may have up to 255 EXEC statements.
What is the stepname on the EXEC statement used for and is it a required parameter?
Answer : Stepname on the EXEC statement is used to name the job step. It is required if subsequent JCL statements refer to it or if one wishes to restart the job from the step; otherwise it is optional. Stepname are recommended and should have unique names. The names must begin in column 3 with an alphabetic or national character (A-Z, @$#)
Which parameter is used to name the program in the exec statement?
Answer : The parameter ‘PGM=’ is used to name a program or utility to be executed. For example, to code a program named ‘FIRST’, one would code ‘PGM=FIRST’. For utility named ‘IEBGENER’, it would be coded as ‘PGM=IEBGENER’.
What are the commonly used parameters on the EXEC statement and what do you they mean?Answer : The most commonly used parameters on the EXEC statement are: COND, PARM, REGION, and TIME. They stands for:
1. COND – Specifies conditions to execute subsequent job steps if the previous step(s) fail.
2. PARM – Passes parameter to the job steps.
3. REGION – Specifies the region size to allocate for the job / job step.
4. TIME – Imposes a time limit on the job or job step.
What is the default for the TIME parameter if it is not coded on the EXEC statement?
Answer : If the TIME parameter is omitted from the EXEC statement, the default is 30 minutes of the CPU time.
What is the difference between the JOBLIB & STEPLIB statements?
Answer : The JOBLIB statement is placed after the JOB statement and is effective for all job steps. It cannot be placed in the catalogued procedure. The STEPLIB statement is placed after the EXEC statement and is effective for that job step only. Unlike JOBLIB statement, the STEPLIB cannot be placed in the catalogued procedure.
What can be done to resolve a JCL error that reads ‘DATASET NOT FOUND’?
Answer : Some of the actions one can take to resolve a JCL error ‘DATASET NOT FOUND’ are:
1. One must examine the job log and the allocation/deallocation report and identify the step and DDname involved.
2. Determine whether or not the dataset name does indeed exist on the system.
3. Check the JCL to make sure the dataset name is spelled correctly.
4. If the job has more than one step and the ABEND is not on the first step, check to see if the dataset on the previous step was deleted.
5. Fix the problem and resubmit the job.
Does a ‘DD STATEMENT MISSING’ message normally ABEND the job?
Answer : A DD statement missing message normally does not ABEND the job, but if not fixed it could later cause problems when least expected. It is advisable to determine why this message was generated and take action to rectify the problem.
Parameters COND, REGION, AND TIME can be coded on both the JOB and the EXEC statements. What are the differences between using them on the JOB versus the EXEC statements, and in which statements are they commonly used?
Answer : Parameters COND, REGION, AND TIME coded on the JOB statement will be in effect for the entire job. When used on the EXEC statement, they will be in effect for that job step only. The COND parameter is normally used on the EXEC statement. The REGION parameter is not normally used unless a particular program requires a lot of storage and it is necessary to override the installation’s REGION Default. If the REGION parameter is used on the both JOB and EXEC statements, then the REGION parameter from the JOB statement will be in effect. The TIME parameter is most often used on the JOB statement.
Explain how the virtual storage works in MVS/SP.
Answer : MVS/SP stands for Multiple Virtual Storage / System Program. A major architectural component of virtual storage MVS is virtual storage. With virtual storage, storage addresses of the application program are independent of the addresses of the computers central storage. A Hardware feature, paging supervisor, transfers the users virtual storage addresses to the computers central storage addresses during execution. With Virtual Storage, a program needs to occupy only a relatively small amount of central storage. This allows programs to be run whose size exceeds the central storage available on the computer.
What are some of the main features of MVS/XA?
Answer : MVS/XA stands for Multiple Virtual Storage / Extended Architecture. MVS/XA uses 32 bits of addressing. This gives an address space of approximately 2 billion bytes. The extended architecture also consists of more sophisticated I/O channels for faster I/O. Also, a separate version of OS is required. One of the difference is that a program for MVS/XA can go up to 2 billion bytes. Programs running under MVS/SP can go up to
16 million bytes.
What are the “basic architecture” features of MVS/ESA?
Answer : MVS/ESA stands for Multiple Virtual Storage / Enterprises System Architecture. MVS/ESA permits an application to have multiple 2-gigabyte address spaces. This allows huge applications to be segregated into functional parts. For ESA, the first address space is called the application space and programs can execute in it. The other address space are called dataspaces and they contain only data. MVS/ESA also has the facility for hyperspaces, which allows temporary data to be stored or retrieved in 4-kbyte blocks under program control. Maximum address space is up to 2 trillion bytes in multiple of 2-billion-byte address spaces.
What is the meaning of the “line”?
Answer : The “line” indicates the maximum address space that is available for the MVS system. For MVS/SP it is 16 million bytes, for MVS/XA it is up to 2 billion bytes, and MVS/ESA is up to 2 trillion bytes in multiple of 2-billion-byte address spaces.
When would a program run “below the line”?
Answer : A program would run “below the line” if it did not exceed the address space available.
When would a program run “above the line”?
Answer : A program would run “above the line” if it required more than 16 megs or if it is competing with other programs which are using the same address space. Special Parameters must be set for compilation and linkage editing in order for a program to run above the 16-meg line.
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