Many applications require the generic JVM argument
-Djava.awt.headless to be set to false.
This is not advisable for the z/OS platform. There are several
variables in the variables.xml file that Application Server does not allow
to be changed and this is one of them. Since this is a JVM setting,
Application Server has to put in some limitations in case it interferes
with Application Server code.
Headless processing with AWT API means there is a dependency of the API
on X Servers to process graphics. Since the native z/OS system does not
have an X Server running, modifying that property to be false can cause
unpredictable results. Therefore, Application Server for z/OS tries to
prevent customers from overriding that property. So even though it can be
successfully set, it may not actually override the default value (which in
this case happens to be true). In Distributed platforms however, since
native X Servers are often available, this restriction may not be
present.
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