A useful link to post periodically, which discusses register clearing on slide 51:
https://community.ibm.com/HigherLogic/System/DownloadDocumentFile.ashx?DocumentFileKey=d1cdb394-0159-464c-92a3-3f74f8c545c4 Jim Mulder z/OS Diagnosis, Design, Development, Test IBM Corp. Poughkeepsie NY
