Resizing a native VSAM file which is used in IDMS
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Resizing a native VSAM file which is used in IDMS

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Article ID: 23678

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Updated On:

Products

IDMS IDMS - Database

Issue/Introduction

This article describes how to resize native VSAM files that are defined to an IDMS CV.

Environment

Release: All supported releases.

Resolution

A native VSAM area, even in IDMS, is first and foremost a native VSAM file. All that is done in IDMS is define a segment/area/file set up to tell IDMS the physical attributes of the native VSAM file. There must be at least one record in the dataset. Don't change the CISIZE of the VSAM-files during this process, since its size corresponds to the page size of the IDMS buffer for that file.

The complete way to resize (enlarge the file) is the following:

  1. Change the number of pages in the IDMS area definitions for the native VSAM files so that the number of pages relates to the number of records in the new VSAM file definitions.
  2. Re-compile the DMCL.
  3. Take the CV down.
  4. DELETE/(re-)DEFINE the native VSAM file(s).
  5. Copy the records into the native VSAM file. It may be necessary to put at least one record in the native VSAM file to allow IDMS to open them properly (REPRO).
  6. Bring the CV up.
  7. Issue the DCMT DISPLAY AREA area-name command to confirm that the file is in UPDate mode to the CV and that the new page range is correct according to what it was changed to.

In the event that the file is being reduced in size and the change is to be done without cycling the CV, the following steps are sufficient:

DCMT VARY AREA area-name OFFLINE
DCMT VARY FILE file-name DEALLOCATE

  *NOTE: It is not possible to vary all native VSAM files DEALLOCATE with DCMT V SEGMENT.  They must be varied separately with DCMT VARY FILE.

Perform the necessary VSAM steps (DELETE/DEFINE/REPRO)

DCMT VARY AREA area-name ONLINE

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