A z/OS® system usually contains additional, priced products that are needed to create a practical working system.

For example, a production z/OS system usually includes a security manager product and a database manager product. When talking about z/OS, people often assume the inclusion of these additional products. This assumption is normally apparent from the context of a discussion, but it might sometimes be necessary to ask whether a particular function is part of "the base z/OS" or whether it is an add-on product. IBM® refers to its own add-on products as IBM licensed programs.

With a multitude of independent software vendors (ISVs) offering a large number of products with varying but similar functionality, such as security managers and database managers, the ability to choose from a variety of licensed programs to accomplish a task considerably increases the flexibility of the z/OS operating system and allows the mainframe IT group to tailor the products it runs to meet their company's specific needs.

We won't attempt to list all of the IBM licensed programs for z/OS (hundreds exist); some common choices include:

Security system

z/OS provides a framework for customers to add security through the addition of a security management product (IBM's licensed program is Resource Access Control Facility or RACF®). Non-IBM security system licensed programs are also available.

Compilers

z/OS includes an assembler and a C compiler. Other compilers, such as the COBOL compiler, and the PL/1 compiler are offered as separate products.

Database management systems

DB2® for z/OS and Information Management System (IMS™) are two examples of database management systems. Other types of database products are also available.

Transaction processing facility

IBM offers several, including:

• Customer Information Control System (CICS®)
• Information Management System (IMS)
• WebSphere® Application Server for z/OS

Sort program

Fast, efficient sorting of large amounts of data is highly desirable in batch processing. IBM and other vendors offer sophisticated sorting products.

A large variety of utility programs

For example, the System Display and Search Facility (SDSF) program that is used to view output from batch jobs is a licensed program. Not every installation purchases SDSF; alternative products are available.