What defines a VSAM?

What defines a VSAM?

A VSAM cluster is a logical definition for a VSAM data set and has one or two components:

  1. The data component of a VSAM cluster contains the data records.
  2. The index component of a VSAM key-sequenced cluster consists of the index records.

What is a cluster in mainframe?

CLUSTER, the space amount is divided between the data and index components. The division can be done based on the control interval size, record size, device type, and other data set attributes. DATA, the entire amount specified is allocated to the data component.

How do I create a VSAM file?


  1. Locate the JCL to create the VSAM data sets.
  2. Modify the JCL and access method services commands.
  3. Run both jobs to create and populate the data sets.
  4. Use the CICS Explorer® to create a FILE definition for the catalog file.
  5. Use the CICS Explorer to create a FILE definition for the configuration file.

How do you allocate a VSAM dataset?

Select the MVS Files subsystem of a remote system connection. Right-click and select Menu > Allocate VSAM Data Set. Note: You can also press Ctrl+4 to allocate a new VSAM data set.

What is IDCAMS?

IDCAMS stands for Integrated Data Cluster Access Method Services. IDCAMS utility is used to create, modify and delete the VSAM datasets.

How does VSAM define keys?

Keys parameter is defined only in key-sequenced (KSDS) files. It specifies the length and offset of primary key from first column. The range of value of this parameter are from 1 to 255 bytes. Value in READPW parameter specifies the password of read level.

What is a base cluster in VSAM?

Building Index BLDINDEX reads all the records in the VSAM indexed data set (or base cluster) and extracts the data needed to build the alternate index. INDATASET is used to specify the VSAM Cluster Name and OUTDATASET is used to specify Alternate Index Name.

What is the purpose of the Verify function of IDCAMS?

VERIFY command is used to verify the status of the dataset when the job terminates abnormally and a VSAM dataset is not closed, the catalog entry for the dataset is flagged to indicate that the dataset may be corrupt.

What are the idcams commands that can be used for VSAM?

VSAM – Commands

  • Alter.
  • Repro.
  • Listcat.
  • Examine.
  • Verify.

How do I view VSAM file attributes?

LISTCAT command in VSAM is used to view the properties of VSAM file like volume details, space details, path details, and catalog details. LISTCAT can list many properties like cluster, data, index, spae details, history, volume and much more.

What is free space in VSAM?

FREESPACE. Freespace specifies the percentage of free space to reserve for the control intervals (CI) and control areas (CA) of the data component. The default value of this parameter is zero percentage.

What is control interval in VSAM?

Control Intervals (CI) in VSAM are equivalent to blocks for non-VSAM data sets. In non-VSAM methods, the unit of data is defined by the block. VSAM works with logical data area which is known as Control Intervals. Control Intervals are the smallest unit of transfer between a disk and the operating system.

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