Chapter 2. Overview of the IMS Product

IMS consists of three components:

• The Database Manager (IMS DB)

• The Transaction Manager (IMS TM)

• A set of system services that provide common services to IMS DB and IMS TM

Known collectively as IMS DB/DC,^[1] the three components create a complete online transaction processing environment that provides continuous availability and data integrity. The functions provided by these components are described in more detail later in this book.

^[1] The "DC" in DB/DC is a left-over acronym from when the Transaction Manager was called the Data Communications function of IMS.

IMS delivers accurate, consistent, timely, and critical information to application programs, which deliver the information to many end users simultaneously.

IMS has been developed to provide an environment for applications that require very high levels of performance, throughput, and availability. IMS uses many of the facilities offered by the operating system and hardware. Currently, IMS runs on z/OS and on zSeries hardware.

IMS TM and IMS DB can be ordered and paid for separately if the functions of one component are not required. The appropriate system services are provided for the component ordered. When IMS DB is ordered by itself, it is called DB control (DBCTL). When IMS TM is ordered by itself, it is called DC control (DCCTL).

IMS is developed so that each new release of IMS is upwardly compatible, meaning that applications that were written for a previous release of IMS will run without modification (in most cases) with a new release. In this way, IMS protects the investment that our customers have made in their applications.

To accommodate the changing requirements of IT systems, many new features have been added to IMS over the years. In many instances, older features have been wholly or partially superseded by the newer features that provide better functionality.

Application programs that are written to use IMS functions can be written in a number of programming languages: Assembler, C/C++, COBOL, Java, Pascal, PL/I, and REXX. These applications access IMS resources by calling a number of standard IMS functions through standard application programming interfaces (APIs):

• DL/I

• Java database connectivity (JDBC)

In This Chapter:

• "IMS Database Manager"

• "IMS Transaction Manager" on page 12

• "IMS System Services" on page 13

• "IMS Documentation" on page 13

• "Hardware and Software Requirements for IMS" on page 13