Browse Prior Art Database

Method to maintain IMS database description files to be consistent with actual database structure

IP.com Disclosure Number: IPCOM000012249D
Original Publication Date: 2003-Apr-23
Included in the Prior Art Database: 2003-Apr-23
Document File: 3 page(s) / 33K

Publishing Venue

IBM

Abstract

Disclosed is a method to maintain IMS database description files, that are application control block (ACB) and database description (DBD), to be consistent with actual database structure. The method is consist of the following two mechanisms: 1. A mechanism that automatically saves the database description (DBD) file to be used by the database initial load program or the database restructure program. 2. A mechanism that automatically re-generates either or both of the database description (DBD) file and/or the application control block (ACB) file from the DBD file stored by the mechanism 1.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 40% of the total text.

Page 1 of 3

THIS COPY WAS MADE FROM AN INTERNAL IBM DOCUMENT AND NOT FROM THE PUBLISHED BOOK

JP820020835 Koichiro Kato/Japan/IBM Toshikazu Takahashi, Fumitaka Uruma

  Method to maintain IMS database description files to be consistent with actual database structure

1.Database description files and actual database structure

Information Management System (IMS) -- IBM's hierarchical database management system software product --, maintains database description files, that describe the structure of hierarchical databases, separated from the database entities themselves. IMS uses two different database description files depending on whether the environment in which application programs are running is batch or on-line. A description file to be used in a batch environment is the database description (DBD) file, and the one to be used in an on-line environment is the application control block (ACB) file. Database users need to create a DBD file first to define the structure of the database, then to generate an ACB file from the DBD file with the process known as ACBGEN. At the beginning, the database structure information contained in the DBD and ACB files is consistent with the actual database structure itself, but sometimes they get discrepancies caused by the following reasons:

An old database description file (ACB or DBD) is mistakenly used for the database that has already been restructured. A database description file (ACB or DBD) to be used in a test system is mistakenly used in a production system.

If an application program uses such incorrect database description files to get access to a database, it could result database corruption.

2.Limitation of existing techniques

There are some existing programs to protect databases from corruption by detecting differences between the following two:

The database description file the application program is using to get access to a database The database description file that was used to load the database or to restructure the database

There also are existing programs to check consistency between the contents of the ACB and DBD files. When you use these programs, however, you need to do the following things manually after the program detects inconsistency, that are:

to identify whether the ACB or DBD file is incorrect (because the programs report only the difference) to re-generate the database description file to replace the incorrect one, from the correct one within the ACB-DBD pair, by ACBGEN (from DBD to ACB) or a DBD reverse engineering tool (from ACB to DBD).

These existing techniques have the following limitations:

The process is hard to automate, because you need to identify whether the ACB or the DBD file is correct before re-generate the incorrect one to recover consistency between them. Sometimes, both of the ACB and DBD could be incorrect. In such a case, you need to re-generate the DBD file that correctly contains the actual database structure, from the DBD source you luckily stored ago, and re-...