The discussion so far has been about SYSTEM-Managed Duplexing. What hasn't been discussed is USER-Managed Duplexing. The latter (DB2 Group Buffer Pools only so POSSIBLY not relevant to the Original Poster) generally sees far fewer requests to the Secondary structure.
Which is why customers are less leery of User-Managed Structure Duplexing than System-Managed. Cheers, Martin Martin Packer, zChampion, Principal Systems Investigator, Worldwide Banking Center of Excellence, IBM +44-7802-245-584 email: martin_pac...@uk.ibm.com Twitter / Facebook IDs: MartinPacker Blog: https://www.ibm.com/developerworks/mydeveloperworks/blogs/MartinPacker From: Mark Brooks <mabr...@us.ibm.com> To: IBM-MAIN@listserv.ua.edu Date: 11/10/2013 21:59 Subject: Re: Coupling Facility Structure Duplexing Sent by: IBM Mainframe Discussion List <IBM-MAIN@listserv.ua.edu> Hi, Duplexed requests are more costly than simplex requests. Generally applications "feel" this most significantly via longer service times. In terms of comparing the actual CPU cost to the two CF's for processing a duplexed requests, the correct answer is "it depends". It depends on what operations the application is driving to the structure and the z/OS implementation. Some examples of the sorts of things that come into play here: - For many operations, the same command will be sent to both facilities. Here I'd expect equal CPU cost. - For some operations, the commands sent to the two structures are different. For example, if the application is doing a "read and delete" of an object, both CF's need to delete the object but only one of them needs to do the work to send back the data. - For some operations, z/OS issues a simplex request to one of the structure instances to determine what objects are to be processed, and then drives duplex commands to both CFs to process those objects. Again, those duplexed commands will generally be identical, but I would not be surprised if there are cases where they are different. In current practice, it is reasonable to assume that the CF CPU cost of for the secondary structure instance is no worse than the cost for the primary instance. Mark A. Brooks z/OS Sysplex design and development 845-435-5149 T/L 8-295-5149 Poughkeepsie, NY mabr...@us.ibm.com ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
