The Call Hierarchy view is a tree graphic that displays functions and procedures. This view provides a way to navigate a large or complex PL/I file that contains many procedures and assists you with determining the call flow between the procedures. The Call Hierarchy view provides information from both a called and caller perspective.

The Call Hierarchy view contains the following toolbar buttons for filtering the contents of the view.
Callee Hierarchy:
Displays in the view only the procedures that called the highlighted
procedure.
Caller Hierarchy:
Displays in the view only the procedures that are called by the highlighted
procedure.
View menu: Shows a list of functions
to perform in the Call Hierarchy view. In addition
to the Caller Hierarchy and Callee Hierarchy view, you can select
to hide or show built in functions.