Home > Articles > Security > Network Security

  • Print
  • + Share This
This chapter is from the book

1.3 Job Control Language (JCL)

Entering commands from TSO is one way to accomplish tasks in z/OS, but many other ways exist. One of the most popular and powerful ways is to create files that contain lists of things to do. These lists are called batch jobs and are written in z/OS Job Control Language (JCL), which fulfills roughly the same role as shell scripting languages in UNIX.

1.3.1 Introduction to JCL

JCL is a language with its own unique vocabulary and syntax. Before you can write your first JCL, you need to understand a few z/OS concepts and facilities.

We use JCL to create batch jobs. A batch job is a request that z/OS will execute later. z/OS will choose when to execute the job and how much z/OS resources the job can have based upon the policies that the system administrator has set up. This is a key feature of z/OS: z/OS can manage multiple diverse workloads (jobs) based upon the service level that the installation wants. For example, online financial applications will be given higher priority and, therefore, more z/OS resources, and noncritical work will be given a lower priority and, therefore, fewer z/OS resources. z/OS constantly monitors the resources that are available and how they are consumed, reallocating them to meet the installation goals. We could spend volumes describing just this one feature of z/OS, but this book is supposed to be about security, so we won't.

In your batch job, you will tell z/OS this information:

  • You'll give the name of your job, with a //JOB statement
  • You'll specify the program you want to execute, with a //EXEC PGM=<program name> statement
  • If your program uses or creates any data, you'll point to the data using a //DD statement.

Listing 1.1 shows a trivial JCL job. Don't worry about executing this job, or about the exact meaning of each word—we explain them later in this chapter.

Listing 1.1. Trivial Batch Job

//MARKNJ JOB CLASS=A,NOTIFY=&SYSUID,MSGCLASS=H
//       EXEC PGM=IEFBR14

This job executes an IBM-provided z/OS program called IEFBR14. This is a dummy program that tells z/OS "I'm done and all is well." It requires no input and produces no output other than an indication to the operating system that it completed successfully.

You can also run TSO as a batch job by using JCL to tell z/OS this information:

  • The name of the job
  • The program to run, which is the TSO interpreter IKJEFT01
  • Where to get the input for IKJEFT01 and the commands that you want to execute
  • Where to put the output from IKJEFT01, the output from TSO, and the commands that you execute

Listing 1.2 shows a batch job that runs TSO to send a message.

Listing 1.2. Batch Job That Sends a Message Using TSO

//TSOJOB  JOB CLASS=A,NOTIFY=&SYSUID,MSGCLASS=H
//        EXEC PGM=IKJEFT01
//SYSTSPRT DD SYSOUT=*
//SYSTSIN  DD *
SEND 'Hello, World' U(ORIPOME)
/*

1.3.2 Data Sets

To submit a batch job, you need to understand data sets. As the name implies, a data set is a set or collection of data. Data sets are made up of records. To improve performance, records can be gathered together into blocks. Data sets fill the same function as files and directories in UNIX and Windows.

When you create a data set, you assign it a name. The name can be up to 44 characters long and consists of multiple parts, separated by dots (.). Each part can be up to eight characters. In a RACF-protected system, the first qualifier is either a user ID or a group name. We discuss group names in Chapter 2, "Users and Groups."

Examples of valid data set names are

  • MARKN.BOOK.CNTL
  • ORI.LONG$$$$.DATASET.NAME.WITHLOTS.OFQUALS
  • SYS1.PARMLIB

Examples of data set names that are invalid are

  • MARKN.QUALIFIERTOOLONG.CNTL (the middle qualifier is longer than eight characters)
  • ORI.THIS.DATA.SET.NAME.IS.WAY.WAY.WAY.TOO.LONG (the total data set name is longer than 44 characters)

The act of creating a data set is called data set allocation. To allocate a data set, you need to tell z/OS a few things about the data set:

  • The length of records within the data set expressed in bytes (often called the LRECL)
  • The expected size of the data set
  • If records are to be blocked, the number of bytes in the block (called the BLKSIZE)
  • The organization of the data set (referred to as the DSORG)

Data set organization requires a little explanation. z/OS allows you to define a data set that is partitioned into multiple "mini data sets" called members. This type of data set is called a partitioned data set (PDS). PDSs contain a directory that tells z/OS the name of the member as well as how to locate the member, similar to directories under UNIX, Windows, and Linux. Much of the work that you do in z/OS involves the use of PDS data sets, or their more modern version, the extended PDS called the PDSE or library.

In contrast to UNIX, Linux, and Windows, z/OS requires you to specify the maximum size of each data set, for two reasons. The first is historical—z/OS is backward compatible and can run applications that were developed 40 years ago when disk space was at a premium. The second reason is that z/OS is designed for high-availability applications. When you specify the maximum size of each data set, you can ensure that the important data sets will always have the disk space they need. For simple data sets, such as the ones that we are discussing here, the allocation consists of two parts:

  1. The initial size of the data set is called the primary extent. This is the amount of space that z/OS reserves for the data set right now. If you think that your data set might grow in size later, you can specify the size of the secondary extents.
  2. If the data set is expected to grow beyond its initial size, additional allocations of disk storage can be given to the data set by specifying the size of the secondary extent. If the primary extent of your data set fills up, z/OS allocates the secondary extent up to 15 times. This allows your data set to grow gradually up to the maximum data set size.

When defining the size of the primary and secondary extents, you can do it in bytes or based on the device geometry in units of space called tracks or cylinders. Understanding these two terms requires understanding how a disk drive works. A disk drive consists of a set of rotating metallic platters upon which data is stored magnetically. Data is written on the disk in sets of concentric circles. Each of these circles is called a track. If you project that track from the top of the stack of platters to the bottom, you have created a cylinder. It is faster to read information that is stored in the same cylinder than information that is spread across cylinders.

1.3.3 Using ISPF to Create and Run Batch Jobs

Before we can create and submit a batch job, we need to create a data set to hold it. The simplest way to allocate a data set is to use the Interactive System Productivity Facility (ISPF).

1.3.3.1 Data Set Creation

Getting into ISPF is very simple: just type ISPF on the TSO command line. ISPF enables you to perform many common z/OS tasks from a full-screen interactive dialog. You move about the ISPF dialogs by specifying the number of the dialog that you want to use. For example, Utilities is option 3. You can then choose the suboption, which enables you to define and delete data sets. That's option 2. We often combine these two and type them as ISPF option 3.2.

As you can see in Figure 1.8, each ISPF panel presents the list of options that you can select. When you get familiar with ISPF, you can use ISPF's fast-path feature and specify =3.2 from any ISPF panel to have ISPF take you directly to the data set allocate and delete panel.

Figure 1.8

Figure 1.8 Main menu of ISPF

Select option 3.2 and press Enter (or the right Ctrl key). ISPF now takes you to a panel where you can allocate and delete data sets. Type A as the option, your user ID as the project (ORIPOME in the screenshot), RACFBK as the group, and CNTL as the type, as shown in Figure 1.9. By convention, CNTL is used for data sets that store JCL jobs, which correspond roughly to shell scripts or batch files.

Figure 1.9

Figure 1.9 Step 1 in data set creation

To allocate the data set, you need to tell z/OS this information:

  • The expected size of your data set. We'll be adding other members to this partitioned data set, so let's give it an initial size (primary allocation) of ten tracks and allow it to grow five tracks at a time (secondary allocation). Remember that z/OS uses the secondary allocation 15 times before the data set reaches its maximum size.
  • The length of each record in your data set. One of the most common record lengths in z/OS is 80 bytes, which is what we will use for our first few data sets.
  • The size of each block. For performance reasons, you might want to tell z/OS that whenever it reads a record, it should read a group of them. That way, when you read the next record, it will already be in memory. Every time z/OS reads from the disk, it reads an entire block. The block size that you select also affects the efficiency of the records stored on the disk drive. If you specify 0, z/OS calculates the best block size for the device upon which the data set is placed.
  • The number of directory blocks. When a data set is a partitioned data set, you need to tell z/OS how much space on the data set should be reserved for the directory. Each directory block has enough space to hold the information for about five members. We'll specify 20 blocks, which will give us plenty of space for new members.
  • The organization of the data set. Many different types of data sets exist. For our purposes, we'll be working with two types of data sets: normal data sets (called sequential data sets) and partitioned data sets. For this data set, specify PDS for a partitioned data set. Sequential data sets are similar to files under other operating systems. Partitioned data sets contain multiple members, distinguished by name. Each member is similar to a file, so the entire partitioned data set is similar to a directory.

After you have typed all this information, your panel should look similar to Figure 1.10. Press Enter to create the data set. ISPF responds by representing the Data set utility panel with Data Set Allocated highlighted in the upper-right corner.

Figure 1.10

Figure 1.10 Step 2 in data set creation

1.3.3.2 Editing Data Set Members

When the data set is created, go to the ISPF editor. To do this, enter =2 on any command line. This is the ISPF "fast path" to the ISPF edit panel, which is option 2 from the main ISPF menu. On this panel, specify the name of the data set that you just allocated. Because you are editing a PDS, you need to specify either the name of an existing member or the name of a member that you want created, as shown in Figure 1.11. In this example, we're creating a member named HELLOW.

Figure 1.11

Figure 1.11 ISPF edit panel

After you press Enter, ISPF creates the member and places you in the ISPF editor. At this point, type the JCL shown in Listing 1.2. You need to type it on the lines that start with '''''', under the blue asterisks (*), as shown in Figure 1.12. Remember to change ORIPOME to your own user ID. Traditionally, JCL lines use the eight characters after the // for identifiers or leave them empty when no identifier is required. That is the reason, for example, that the word EXEC on the second line starts on the same column as the word JOB on the first line. The JCL would work with just one space, but it is more readable this way.

Figure 1.12

Figure 1.12 The editor after typing the batch job

After this is done, press Enter. ISPF saves your changes and replaces the quotes on the left with line numbers.

At this point, you're ready to submit your job. Type SUBMIT on the command line, and your batch job is submitted to the job entry subsystem at your installation. You will get a confirmation message with the job number, as shown in Figure 1.13.

Figure 1.13

Figure 1.13 Job submission confirmation message

Your installation has a policy for executing batch jobs, and that policy determines when your batch job is executed. After it has executed, you can view the output of the job. When your job executes, it sends a message to your TSO user ID. If you are logged on and are accepting messages, the message appears as your batch job executes. If you are not logged on or are not accepting messages, it is saved and displayed when you next log on.

When you see the confirmation message, press Enter again. In all likelihood, your job will have already executed and you will see the message, as well as a job confirmation message, as shown in Figure 1.14.

Figure 1.14

Figure 1.14 The message the job sent

When you are done with ISPF, enter =X on the command line to tell it to exit. If you get a log data panel, such as the one in Figure 1.15, select option 2 to delete the log. You can then use LOGOFF to exit TSO.

Figure 1.15

Figure 1.15 The log data panel when leaving ISPF

1.3.4 JCL Syntax

Now that you've run the JCL and seen that it works, let's review Listing 1.2 line by line and explain exactly what it does.

First, you'll notice that most lines start with two slashes. The two slashes mark a line as part of JCL. Lines that do not contain those slashes, such as the last two lines in this job, are usually embedded input files.

//TSOJOB  JOB CLASS=A,NOTIFY=&SYSUID,MSGCLASS=H

This line is the job header. It defines a job called TSOJOB. The CLASS parameter specifies the job's priority, the maximum amount of resources the job is allowed to consume, and so on. A is a good default in most installations, at least for the short jobs we'll use in this book.

The NOTIFY parameter specifies that a user should be notified when the job ends. It could be the name of a user to notify, but here it is &SYSUID, which is a macro that expands to the user who submits the job.

The MSGCLASS parameter specifies that the output of the job needs to be held. This makes it accessible afterward, as you will see in Section 1.3.5, "Viewing the Job Output."

//        EXEC PGM=IKJEFT01

This line starts an execution step—a step in the batch job that runs a program. It is possible for these steps to be named using an identifier immediately after the two slashes. However, this is a very simple job, so there is no need to identify this stage.

The program that this step executes is IKJEFT01, which is the TSO interpreter.

//SYSTSPRT DD SYSOUT=*

This line is a data definition. It defines the data stream called SYSTSPRT, which is the output of TSO. SYSOUT=* means that this data stream will go to the standard output of the job. In the next section, you will learn how to get to this output to read it.

//SYSTSIN  DD *

This line is another data definition. It defines SYSTSIN, which is the input to the TSO interpreter. The value * means that the text that follows is the data to be placed in SYSTSIN.

SEND 'Hello, World' U(ORIPOME)
/*

This is the input to the TSO interpreter. The first line is a command, the same "Hello, World" command we executed in Section 1.2.3, " 'Hello, World' from TSO." The second line, /*, is a delimiter that means the end of the file.

1.3.5 Viewing the Job Output

One of the outputs from your batch job was the "Hello, World" that was sent to your TSO ID. Your batch job produced other output as well. What happened to that output? It waits in the system until you or your system administrators tell the system what to do with it.

When you submitted the batch job, it was handed over to the job entry subsystem (JES). JES is responsible for scheduling the job, allocating some of its resources, and managing the job's input and output.

IBM provides job entry subsystems: JES2 and JES3. Most of the z/OS environments use JES2, so our examples are oriented toward it. For those of you who are using JES3, equivalent services exist there.

One of the most popular ways to view the output of your job is to use the IBM System Display and Search Facility (SDSF) program product. You start up SDSF either as a TSO command (SDSF) or as a dialog from within ISPF. In most installations, SDSF is option S from the ISPF Primary Options menu.

From the ISPF Primary Options menu, select the SDSF option, which brings you to the SDSF Primary Option menu, shown in Figure 1.16. On this panel, the options that are presented depend upon your level of authorization: The more things you are authorized to do, the more options you'll see presented by SDSF on the panel.

Figure 1.16

Figure 1.16 The SDSF Primary Option menu

The job's output is in the output queue. Type O to enter the output queue, find your job, and type S next to it to open the output, as shown in Figure 1.17. If necessary, you can scroll down using F8 or up again using F7.

Figure 1.17

Figure 1.17 The job's output in the output queue

The top part of the output, shown in Figure 1.18, tells when the job started, when it ended, which user ID was assigned to the job, and other job statistics. JES also displays the JCL. Scroll down a page to see more system-generated messages telling you about the resources allocated for your job. You can scroll up (F7), down (F8), left (F10), and right (F11).

Figure 1.18

Figure 1.18 The first part of the job's output

The real output of the job is in the last four lines of the job, shown in Figure 1.19. These lines show where we see the batch version of TSO displaying the READY prompt, the echoing of the "Hello, World" command, TSO's READY response, and the generated END statement.

Figure 1.19

Figure 1.19 The output of the job's TSO interpreter

1.3.5.1 Filtering Jobs

A large z/OS installation can have many jobs running at the same time. It is possible to use filtering to see only the jobs that are relevant to you.

To see the current filters, run this command inside SDSF:

SET DISPLAY ON

To filter, enter the name of the field to filter (prefix in the job name, destination, owner, or sysname) and the value. For example, this command filters for jobs that start with L.

PREFIX L*

After this command, SDSF will show only those jobs that start with L, as you can see in Figure 1.20.

Figure 1.20

Figure 1.20 Filtered job list in SDSF

To remove the filter, run this command:

PREFIX
  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020