2. PLANNING › 2.2 Supported MVS Data Structures › 2.2.4 Integrated Catalog Facility (ICF) Support

2.2.4 Integrated Catalog Facility (ICF) Support

VCC supports the Integrated Catalog Facility (ICF).  It reads
ICF Basic Catalog Structures (BCSs) and VSAM Volume Data Sets
(VVDSs) to collect and record the following information:

    o  VSAM data set information
    o  VSAM alternate index information


ICF Catalog Structure Overview

The ICF catalog structure is comprised of two components:
the BCS and the VVDS.

The BCS

A Basic Catalog Structure is a standard VSAM key-sequenced
data set with spanned records.  It contains the volume, data
set security, ownership, and association information for VSAM
data sets and ICF catalogs.  For VTOC data sets, the BCS
contains extent information.

The VVDS

A VSAM Volume Data Set is a standard VSAM entry-sequenced
data set with 4K control intervals.  It physically resides on
the same volume as the VSAM data sets that are defined in it,
and contains the dynamic characteristics of these data sets.
Up to 36 BCSs can point to one VVDS; therefore the concept of
VSAM volume ownership no longer exists in the ICF catalog
structure.  A VVDS is identified by the reserved data set
name SYS1.VVDS.Vvolser.  If you use the DFSMS (System Managed
Storage) facility, the VVDS will also contain SMS related
information for VTOC data sets residing on the volume.

Differences Between ICF Catalogs and VSAM Catalogs

In addition to the structural differences between ICF
catalogs and VSAM catalogs, the following additional
differences should be noted:

    o  ICF catalogs can be defined with all attributes that
       relate to VSAM key-sequenced data sets.  This includes
       tuning parameters that were not available for VSAM
       catalogs.

    o  VSAM data spaces are no longer supported in ICF
       catalogs.

    o  As noted previously, the concept of volume ownership
       no longer exists in the ICF catalog structure.

    o  Truename records no longer exist, resulting in faster
       catalog searches.

    o  Multiple ICF catalogs can reside on the same volume.

    o  ICF catalogs can coexist with VSAM catalogs and OS
       CVOLs.  The system master catalog can be either a VSAM
       catalog or an ICF catalog and can point to either VSAM
       or ICF user catalogs.