HGPR
Using HGPR(NOPRESERVE) omits the saving/restoring of the high half of 64-bit general purpose registers, which will improve performance. If your calling programs are Enterprise COBOL, Z/OS XLC/C++, or Enterprise PL/I generated code, you can use the NOPRESERV.
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HGPR(PRESERVE) is the slowest. PRESERVE is the default setting.
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HGPR(NOPRESERVE) is the fastest.