Service Library 400 is a library of services (C++) that provides System i with functionality for Windows, Linux and UNIX. The library comprises all relevant interfaces like database access, dialog interface, printer interface, system APIs, and over 200 CL commands including all pertinent object types such as queues, data areas, spool files, libraries, messages, etc. The library can be used in conjunction with C, C++, OCC, EGL, Micro Focus Cobol and Java.

System i applications typically use a number of i5OS-specific functionalities and can therefore only be ported with a great deal of effort. There are two solution methods in everyday practice.

The first approach entails the removal of all i5OS-specific functionalities from the application and their substitution with standard interfaces (if at all possible). This requires switching database access from batch-oriented to SQL, replacing the 5250 dialog, all CL commands, QAPIs, multi-format files, member concepts and much more.

With the second approach, parts of these necessary functionalities are duplicated in the target system. Due to the high degree of complexity of i5OS functionality, this task can easily take a number of development years. PKS has presented a global solution to this problem with the Service Library 400. Almost all pertinent interfaces, system objects, APIs, CL commands, etc. display a high degree of performance in this library and are modularly implemented in C++.  The library essentially encompasses the following functionalities: