The simplest rule is to check the hardware feature requirements for the lowest level of the operating system that you might need to support. For z/OS, the table is as follows:
https://www.ibm.com/docs/en/zos/3.1.0?topic=system-identifying-server-requirements In this table, running z/OS 2.1 or above requires the Store Clock Fast facility, so you are certainly safe if you only need to run with currently supported z/OS levels (of which I believe the lowest is currently z/OS 2.5). Jonathan Scott -----Original Message----- From: IBM Mainframe Assembler List <ASSEMBLER-LIST@LISTSERV.UGA.EDU> On Behalf Of Mario Bezzi Sent: 11 April 2025 07:51 To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Store-Clock-Fast Facility PoP states "The store-clock-fast facility *may* be available on a model implementing z/Architecture." The "may" word forces my performance sensitive code to go through additional controls before using STCKF, which sort of defeats the purpose of the instruction. STCKF was first introduced in 2005 and has been available in any CPC generation since then. If I could rely on it being always available I would have less code to run and maintain. Is there documentation stating which facilities are available in a given CPC family? What others do? PoP states the same for Transactional-Execution Facility, still IBM started warning long in advance about its withdrawal. Thank you! mario
