About the Authors
Dean H. Meltz
is team lead for IMS Information Development at IBM's Silicon Valley Lab, in San Jose, California. He has been an IBM technical writer for seventeen
, IMS systems specialist with IBM's International Technical Support Organization (ITSO),
Mark Harrington , IMS systems programmer at IBM Global Services, UK, has spent twenty-two years working with IBM mainframes as a developer, application designer, installer, and DBA.
Robert Hain has been an IMS systems programmer for seventeen years. He works for IBM Global Services, Melbourne, Australia, as part of the Telstra Alliance.
Geoff Nicholls , a member of IBM's Worldwide IMS Technical Support Team, works with IMS customers throughout Australia and Asia.
Part I: Overview of IMS
Chapter 1. IMS: Then and Now
Chapter 2. Overview of the IMS Product
Chapter 3. Accessing IMS
Chapter 4. IMS and z/OS
Chapter 5. Setting Up and Running IMS
Chapter 1. IMS: Then and Now
In This Chapter:
History of IMS: Beginnings at NASA
IMS has been an important part of world wide computing since its inception.
On May 25, 1961, United States President John F. Kennedy challenged American industry to send an American man to the moon and return him safely to earth. The feat was to be accomplished before the end of the
In 1966, 12 members of the IBM team, along with 10 members from American Rockwell and 3 members from Caterpillar Tractor,
In April 1968, ICS was installed. The first "READY" message was displayed on an IBM 2740 typewriter terminal at the Rockwell Space Division at NASA in Downey, California, on August 14, 1968.
In 1969, ICS was
Since 1968, IMS:
IMS as a Database Management System
The IMS database management system (DBMS) introduced the idea that application code should be separate from the data. The point of separation was the Data Language/Interface (DL/I). IMS controls the access and recovery of the data. Application programs can still access and navigate through the data by using the DL/I standard callable interface.
This separation established a new paradigm for application programming. The application code could now focus on the manipulation of data without the complications and overhead associated with the access and recovery of data. This paradigm virtually eliminated the need for redundant copies of the data. Multiple applications could access and update a single instance of data, thus providing current data for each application. Online access to data also became easier because the application code was separated from data control.
IMS as a Transaction Manager
IBM developed an online component to ICS/DL/I to support data communication access to the databases. The DL/I callable interface was expanded to the online component of the product to enable data communication transparency to the application programs. A message queue function was created to maintain the integrity of data communication messages and to provide for scheduling of the application programs.
The online component to ICS/DL/I ultimately became the Data Communications (DC) function of IMS, which became the IMS Transaction Manager (IMS TM) in IMS Version 4.