When THREAD(SERIALIZE) is in effect, the following language elements are not supported and are flagged by the compiler with a severe error message (of severity 30):
Use of DDM data areas is not allowed in a multithreaded environment.
It is recommended that you do not use UPSI switches in a multithreaded environment, since it is possible for one thread to set a switch and another thread to set it again before the first thread has checked it.
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