A PropertyFixed exception indicates that an application has requested that the WorkArea service
remove an existing property that has previously been set as fixed. The fixed mode indicates that
the value must exist within the outermost scope at which the property was first set; the property
cannot be deleted without completing the WorkArea. For example, doing a:
userWorkArea.set("key", "value", PropertyModeType.fixed)
userWorkArea.remove("key");
will throw a PropertyFixed exception. However, note that doing a:
userWorkArea.set("key", "value", PropertyModeType.fixed)
userWorkArea.complete();
will succeed; the property is considered fixed only within the boundary of the context into which
it was set.