Easytrieve DD Statements

What a DD Statement Does

In JCL, a DD statement defines a data set or output stream for one job step. The DD name is the label the program uses internally. The DD parameters tell z/OS which dataset to use, how to open it, whether to create or share it, and where output should go. Easytrieve does not bypass this model. Whether you compile with EZTPA00 or run a linked load module, the step still depends on DD allocation succeeding first.

Think of DD statements as plugs and sockets. Easytrieve source names the socket. JCL supplies the plug that fits. If the names do not match, or the plug points to a dataset that does not exist, the connection fails before report logic runs.

Core DD Names in Easytrieve Work

Matching FILE Names to DD Names

In Easytrieve source, a FILE statement declares a logical file. At runtime, the program expects a DD with the same name unless your installation uses a documented exception. This is one of the most common beginner mistakes: the source says FILE CUSTOMER but the JCL allocates CUSTMAST. The names must align.

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FILE CUSTOMER FB(200 2000)
  CUST-ID     1  10  N
  CUST-NAME  11  30  A
 
JOB INPUT CUSTOMER
  PRINT CUST-RPT

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//RUNRPT   EXEC PGM=CUSTREP
//STEPLIB  DD  DSN=PROD.APP.LOADLIB,DISP=SHR
//CUSTOMER DD  DSN=PROD.CUSTOMER.MASTER,DISP=SHR
//SYSPRINT DD  SYSOUT=*
//CUSTOUT  DD  SYSOUT=A

The FILE name CUSTOMER matches the DD name CUSTOMER. The dataset PROD.CUSTOMER.MASTER is the physical file. Easytrieve reads records using the field positions defined in source. If CUSTOMER DD is missing, allocation fails even though CUSTOMER is clearly defined in the program.

Important DD Parameters

DD statements use many parameters. Beginners should understand the ones that appear in nearly every Easytrieve job.

DISP=SHR is common on input files because the job only reads an existing dataset. DISP=(,PASS) is common on temporary object datasets passed to a later link step. SYSOUT=* routes listing or report output to spool. The exact combination depends on whether the DD is input, output, temporary, or product-related.

Compile DD Example

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//EZTCOMP  EXEC PGM=EZTPA00
//STEPLIB  DD  DSN=DEV.EASYTRIEVE.CBAALOAD,DISP=SHR
//SYSPRINT DD  SYSOUT=*
//SYSIN    DD  DSN=DEV.EZT.SOURCE(PAYRPT),DISP=SHR
//PANDD    DD  DSN=DEV.EZT.MACLIB,DISP=SHR
//SYSLIN   DD  DSN=&&OBJ,UNIT=SYSDA,SPACE=(TRK,(5,5)),DISP=(,PASS)

STEPLIB finds the compiler. SYSIN reads source member PAYRPT. SYSPRINT captures the listing. PANDD supplies macros if the program uses them. SYSLIN receives object code for a later binder step. None of these DDs process business input during compile unless the source itself references runtime files in a compile-and-go flow.

Runtime DD Example

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//PAYRUN   EXEC PGM=PAYRPT
//STEPLIB  DD  DSN=PROD.APP.LOADLIB,DISP=SHR
//         DD  DSN=PROD.EASYTRIEVE.CBAALOAD,DISP=SHR
//PERSNL   DD  DSN=PROD.HR.PERSONNEL,DISP=SHR
//PAYFILE  DD  DSN=PROD.PAYROLL.EXTRACT(+1),DISP=(NEW,CATLG,DELETE),
//            UNIT=SYSDA,SPACE=(CYL,(10,5)),DCB=(RECFM=FB,LRECL=200,BLKSIZE=0)
//SYSPRINT DD  SYSOUT=*
//PAYLIST  DD  SYSOUT=A

Runtime DDs include business input PERSNL, business output PAYFILE, diagnostics SYSPRINT, and report PAYLIST. PAYFILE uses DISP=(NEW,CATLG,DELETE) because the job creates a new generation. PERSNL uses DISP=SHR because the job only reads the existing personnel file. Understanding input versus output disposition prevents accidental dataset deletion or failed creation.

DD Concatenation

Concatenation uses multiple DD statements with the same DD name. For input files, records are read from the first dataset until end of file, then from the next. For STEPLIB, modules are searched in order. For some output cases, concatenation behavior differs and may not be valid depending on dataset type. Always verify site standards before concatenating business output DDs.

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//SALESIN  DD  DSN=PROD.SALES.EAST,DISP=SHR
//         DD  DSN=PROD.SALES.WEST,DISP=SHR

If source says JOB INPUT SALESIN, Easytrieve reads all records from EAST, then all records from WEST, as one logical input stream. This is useful for regional file merges without copying datasets first.

Dummy DDs and Special Cases

Some jobs use DUMMY on a DD when a program expects the DD name but no real data is needed for that run. Other jobs use special DD conventions for sort work, dynamic allocation, or SQL access. Do not invent dummy DDs without understanding program requirements. A missing required DD fails; an unnecessary DUMMY may hide a real allocation problem if used incorrectly.

Common DD Failure Patterns

• DD name in JCL does not match FILE name in Easytrieve source.
• Dataset does not exist or is not cataloged when DISP expects an existing file.
• Security denies read or write access to the executing user or scheduler ID.
• DISP=(NEW,...) fails because a dataset with that name already exists.
• Wrong record format or LRECL causes open failures or data misinterpretation.
• Temporary dataset not passed correctly between compile and link steps.
• Report DD routed to a class or destination nobody checked after the job ran.

Troubleshooting DD Problems

1. Read JES allocation messages for the failing DD name and dataset.
2. Compare JCL DD names with FILE statements in the Easytrieve source.
3. Verify DSN, member name, DISP, catalog status, and security access.
4. Check whether the step is compile or runtime and whether each DD is appropriate.
5. Compare with a recent successful job for the same application.
6. Inspect SYSPRINT only after confirming allocation succeeded or partially succeeded.

Explain It Like I'm Five

DD statements are labels on cords that plug things into the computer. Easytrieve asks for a cord named CUSTOMER. If JCL gives it a cord named CUSTOMER and plugs it into the right file cabinet, everything works. If JCL labels the cord wrong or plugs it into an empty drawer, Easytrieve cannot get the records it needs.

Exercises

1. Write JCL DD statements for one input file and one report output file matching Easytrieve source.
2. Explain the difference between DISP=SHR and DISP=(NEW,CATLG,DELETE).
3. Describe how input DD concatenation changes record processing order.
4. List compile DDs and runtime DDs for the same application.
5. Create a troubleshooting checklist for a DD allocation failure on a business file.