Data Set Component

This chapter describes the data set component of Base.

1. Introduction to Data Sets

A data set is a file of logically linked data records. A record is the basic unit of information used in application programs. The fundamental difference between Unix files and data sets is that Unix files offer only file-level read and write methods, whereas data sets offer record-level read and write methods. Each data set access method stores data in its own data set structure and provides tools for processing the data sets.

Like mainframe data sets, Base data sets are divided into two categories: VSAM data sets and non-VSAM data sets. Base offers different methods for processing each type of data set.

  • VSAM Data Sets

    A utility program that provides efficient access methods to three types of general data sets: sequential, indexed, and direct-access. This utility program was called virtual storage access method (VSAM). The data sets created using VSAM are known as VSAM data set. VSAM was developed by IBM and the functions have been extended and improved later by other mainframe vendors such as Hitachi and Fujitsu.

    In order to rehost mainframe applications to the open system environment, OpenFrame uses DBMS storage technology to support the functions of mainframe VSAM.

  • Non-VSAM Data Sets

    All data sets used before the development of VSAM are called non-VSAM data sets.

    Although OpenFrame uses Unix file system, it provides interfaces for each data set access method.

For more information about data sets, their access methods and TSAM, refer to OpenFrame Data Set Guide.

2. System Tables

Before using Base after installation, system tables must be created in the database. These system tables are automatically created during the installation process. If the system tables are not created correctly, use the of_catalog.sh and of_vtoc.sh scripts to create and delete the tables.

The following are three types of tables required for starting up Base:

  • Catalog Tables

    In mainframes, a catalog data set is composed of a basic catalog structure (BCS) data set and a VSAM volume data set (VVDS). The BCS data set can be regarded as a catalog itself, while the VVDS can be regarded as an extended volume table of contents (VTOC).

    In Base, catalog tables correspond to BCS data sets and VVDS and VTOC provide the functions of VTOC tables.

  • VTOC Tables

    The volume table of contents (VTOC) is a system data set that is present on every volume in mainframe. The VTOC manages the allocation and extension information of a volume.

    VTOC stores the space allocation information of all data sets stored in the volume regardless of cataloging.

The information about initializing Base by using the aforementioned tools is covered in System Initialization. The initialization process includes the configuration of volumes for the OpenFrame system and the creation of catalog data sets. The master catalog is automatically created during the installation. In addition to the master catalog, all other user catalogs can be created with the DEFINE USERCATALOG command of the idcams utility.

For more information about mascat and idcams, refer to OpenFrame Tool Reference Guide.