Classification: Confidential The "spare" ICF engine on the "A" box could be shared between *your* test/production sysplexes.
HTH -----Original Message----- From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of Laurence Chiu Sent: Friday, March 3, 2023 9:34 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Running a Coupling Facility using a CP for a test Parallel Sysplex 0 anyh gotcha's? [CAUTION: This Email is from outside the Organization. Unless you trust the sender, Don't click links or open attachments as it may be a Phishing email, which can steal your Information and compromise your Computer.] The situation. We share a couple of Z13's with another (larger client). Z13 B is where we run our development LPARs and Z13 A is production. For critical business reasons an online application on our production LPAR needs to be highly available and that means in a parallel sysplex. But our outsourcer has told us it cannot be done for the following reasons because there are no spare ICF engines on the host B - all are being used by other CF instances, either to support production Sysplexes or development ones (not ours). Host A does potentially have a spare ICF engine we could use to support a production parallel Sysplex but good practice does recommend you create a test one first of course. I then asked the question, if host A has a spare ICF engine, can't it be used to support a CF to be used by the test Sysplex on B. I was advised this was not possible since there are no spare connections between host A and Host B (Infiniband possibly) so the Sysplex on B could not actually communicate with the CF on A. Our requirement for the Sysplex is primarily to be able to share a VSAM dataset which is hit every time a transaction comes in with a peak of about 99tps. So we would need VSAM RLS to share the dataset records between the two application instances. There is no DB2, CICS or IMS so I think the only structures in the CF are those to support VSAM RLS, maybe some XCF structures and core systems. Knowing that we would only bring up the test sysplex to make sure transactions routed correctly across the two LPARs and most of the time we would have one member of the Sysplex off, I suggested that the test CF could be built using a CP. To this suggestion I received the following (anti) advice - there would be MSU costs (we don't care since we think the MIPS load on the CF would be low). Plus we would ask that the CF be defined with Dynamic Coupling Facility Dispatch and set DYNDISP=THIN. Since that CF is going to be idling most of the time, MSU consumption is not going to be a major cost. - it's strongly recommended not to do this by IBM. Yet when I read this document https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.ibm.com%2Fdownloads%2Fcas%2FJZB2E38Q&data=05%7C01%7Callan.staller%40HCL.COM%7C1962ff1c13d7410924a708db1c617020%7C189de737c93a4f5a8b686f4ca9941912%7C0%7C0%7C638134977066659942%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=78DxD9grmMmrALQNItds2OaQ6Eyuv43mGVh5%2BoeqQnk%3D&reserved=0 the option is discussed in great detail and the only negatives are the incurring of MSU costs and some performance degradation if both a z/OS and CF LPAR are trying to use the same CP at the same time. But this can be managed. - that a CF running on a CP would need a dedicated CP engine and there are no spare engines in host B. That totally flies against the information I have read from IBM docs. Of course for production the CF on host A would be configured to use an ICF engine (or share one) Finally, while I accepted the argument at the time there were no connections between Host A and Host B, further reading suggests that you do not need to dedicate channels for communications but use XCF or by using Infiniband sub channels or sharing the same physical link with more than one Sysplex. Then the issue of running the CF on a CP goes away since I can ask for two CF's to be defined on host A, one for production and one for test and DCFC ensures that that production CF is not impacted by the development one. A lot to digest here but I really want to have some authoritative data in order to refute most of the comments being our outsourcer. 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