DSORG Parameter

Purpose

The DSORG (Dataset Organization) parameter specifies the physical organization of a dataset. It is a critical parameter that defines how data is stored and accessed within a dataset, which in turn determines the appropriate access methods and utilities that can be used with the dataset.

Where DSORG is Used

• In DD statements within JCL
• In IDCAMS utility DEFINE commands
• In the DCB parameter of DD statements
• In the DCB macro for assembler programs
• In TSO ALLOCATE commands
• In dynamic allocation services (SVC 99)

Basic Syntax

DCB Parameter Syntax

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//ddname DD DSN=dataset.name,
//        DCB=(DSORG=xx,...),
//        ...other parameters...

Where xx is the dataset organization code.

IDCAMS DEFINE Syntax

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//SYSIN   DD *
  DEFINE CLUSTER(NAME(dataset.name) -
         ...
         DSORG(xx) -
         ...)
/*

DSORG Values

Special DSORG Codes for System Use

DSORG Usage Examples

Physical Sequential (PS) Dataset

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//DD1      DD DSN=USER.DATA.FILE,
//            DISP=(NEW,CATLG,DELETE),
//            SPACE=(TRK,(10,2)),
//            DCB=(RECFM=FB,LRECL=80,BLKSIZE=8000,DSORG=PS)

This example creates a new physical sequential dataset with fixed-block records.

Partitioned Dataset (PO)

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//SRCLIB   DD DSN=USER.SOURCE.LIB,
//            DISP=(NEW,CATLG,DELETE),
//            SPACE=(CYL,(5,1,10)),
//            DCB=(RECFM=FB,LRECL=80,BLKSIZE=8000,DSORG=PO)

This example creates a new partitioned dataset (library) with directory blocks for member entries.

Direct Access (DA) Dataset

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//DIRECT   DD DSN=USER.DIRECT.FILE,
//            DISP=(NEW,CATLG,DELETE),
//            SPACE=(TRK,(50,10)),
//            DCB=(RECFM=F,LRECL=256,BLKSIZE=256,DSORG=DA)

This example creates a direct access dataset, which allows records to be accessed directly by their key.

VSAM Dataset via IDCAMS

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//STEP1    EXEC PGM=IDCAMS
//SYSPRINT DD SYSOUT=*
//SYSIN    DD *
  DEFINE CLUSTER (NAME(USER.VSAM.KSDS) -
         VOLUMES(VOL001) -
         INDEXED -
         RECORDSIZE(80 80) -
         KEYS(8 0) -
         CYLINDERS(2 1))
/*

For VSAM datasets, you typically use IDCAMS DEFINE commands instead of specifying DSORG=VS directly.

TSO Allocation

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ALLOC F(OUTDD) DA('USER.DATA.FILE') NEW SPACE(1,1) TRACKS -
      DSORG(PS) RECFM(FB) LRECL(80) BLKSIZE(8000)

Example of using DSORG in a TSO ALLOCATE command.

Common DSORG and RECFM Combinations

Technical Details

Access Methods by DSORG

VSAM Dataset Types

While DSORG=VS exists, VSAM datasets are typically created and managed using IDCAMS. VSAM has its own organization subtypes:

• KSDS (Key Sequenced Data Set): Records are organized by key, allowing both sequential and direct access
• ESDS (Entry Sequenced Data Set): Records are organized sequentially by entry order, similar to a PS dataset but with VSAM features
• RRDS (Relative Record Data Set): Records are accessed by their relative record number
• LDS (Linear Data Set): A specialized VSAM dataset accessed as a continuous byte stream

Best Practices

1. Always Specify DSORG: Include DSORG when creating new datasets to ensure proper allocation and organization
2. Match DSORG with Usage: Select the appropriate DSORG based on how the dataset will be accessed and processed
3. Define Complete DCB Parameters: Always specify RECFM, LRECL, and BLKSIZE along with DSORG for proper dataset definition
4. Use VSAM for Indexed Data: For indexed data access, use VSAM KSDS rather than the older IS organization
5. Consider SMS-managed Storage: For SMS-managed datasets, some DCB parameters may be derived from data class definitions
6. Document Special Requirements: If using specialized DSORG types like DAU or PSU, document the reasons for requiring unmovable datasets
7. Use PO for Multiple Related Items: Group related items (like program source code) in PO datasets rather than separate PS datasets

Common Issues and Solutions

Dataset Organization Evolution

JES2 vs JES3 Considerations

The DSORG parameter is generally consistent between JES2 and JES3 environments as it relates to the underlying data management system rather than the job entry subsystem. However, there are some considerations:

Related Concepts

• RECFM Parameter - Record format specification that works with DSORG
• LRECL Parameter - Logical record length, a key companion to DSORG
• BLKSIZE Parameter - Block size specification for efficient I/O
• DCB Parameter - Data Control Block parameters that include DSORG
• VSAM Concepts - Advanced dataset organization beyond basic DSORG
• IDCAMS Utility - Utility for defining and managing datasets, especially VSAM
• DD Statement - Statement where DSORG is typically specified