vsam dataset t

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VSAM Dataset Types

� VSAM Introduction (vsam-introduction.htm) �VSAM ESDS (vsam-esds.htm)

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The VSAM datasets can be divided into three types based on the storage of data and accessing

of data.

The below are the different types datasets

1. Key Sequential Dataset (KSDS).

2. Relative record Dataset (RRDS).

3. Entry Sequential Dataset (ESDS).

4. Linear Dataset (LDS).

The below are the access methods which are used the various types of datasets.

1. Key Sequential Dataset (KSDS) - Indexed Sequential Access

Method(ISAM)

Indexed Sequential Access Method is a method for indexing data for fast retrieval and it was

originally developed by IBM for mainframe computers.

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Queued sequential access method (QSAM) is an access method to read and write datasets

sequentially on Mainframe systems.

QSAM is used both for devices that are sequential, and for data on devices that could also be

addressed directly, such as magnetic disks.

3. Relative record Dataset (RRDS) - Basic Direct Access Method

(BDAM)

Basic Direct Access Method or BDAM is an access method for System/360 and later

mainframes which consists of routines used in retrieving data from, and storing data onto direct

access devices.

4. Linear Dataset (LDS)

Linear Dataset is a byte stream data set which is rarely used by the users.

Let’s discuss about each dataset one by one

KEY SEQUENTIAL DATA SET (KSDS):

KSDS is very commonly used dataset among all datasets of VSAM.

Each record has one or more key fields and a record can be retrieved (or deleted or inserted)

by key value.

KSDS can be accessed sequentially in the inserted order without supplying any key.

KSDS topic can be explained in detail �here (vsam-ksds.htm).

ENTRY SEQUENTIAL DATA SET (ESDS):

ESDS stores records in sequential order.

In ESDS Records can be accessed sequentially based on the order in RBA value.

In ESDS, Records can be accessed randomly by providing RBA value of the desired record.

ESDS topic can be explained in detail �here (vsam-esds.htm).

RELATIVE RECORD DATA SET (RRDS):

RRDS allows retrieval of records by number of the record like record 1, record 2, and so forth.



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� VSAM Introduction (vsam-introduction.htm) �VSAM ESDS (vsam-esds.htm)

numbers.

RRDS topic can be explained in detail �here (vsam-rrds.htm).

LINEAR DATA SET (LDS):

LDS is a byte-stream data set.

LDS is the only form of a byte-stream data set in traditional z/OS files.

LDS used by DB2, z/OS system functions heavily, but rarely used in application programs.

LDS topic can be explained in detail �here (vsam-lds.htm).



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