Nesting of /COPY and /INCLUDE directives is allowed. A /COPY or /INCLUDE member may contain one or more /COPY or /INCLUDE directives (which in turn may contain further /COPY or /INCLUDE directives and so on). The maximum depth to which nesting can occur can be set using the COPYNEST control specification keyword. The default maximum depth is 32.
You must ensure that your nested /COPY or /INCLUDE files do not include each other infinitely. Use conditional compilation directives at the beginning of your /COPY or /INCLUDE files to prevent the source lines from being used more than once.
For an example of how to prevent multiple inclusion, see Figure 4.