Ken, Cache Fast Write and Dasd Fast Write come enabled on your IBM disk. If you are using Copy Services such as Metro Mirror you do need to turn OFF Cache Fast Write, Dasd Fast Write remains on. Our Performance team saw NO impact in turning off Cache Fast Write. Here is the jcl to turn off Cache Fast Write. BTW, you must run the jcl and point to non PPRC volumes such as Utility devices and you must identify one volume per LSS.
//STEP001 EXEC PGM=IDCAMS //SYSPRINT DD SYSOUT=* //SYSIN DD * SETCACHE UNITNUMBER(8034) CFW OFF SETCACHE UNITNUMBER(9034) CFW OFF SETCACHE UNITNUMBER(80D3) CFW OFF SETCACHE UNITNUMBER(90D3) CFW OFF Roger Ecklund UnitedHealth Technologies Mainframe Storage Management Office: 763-744-1893 Cell: 952-237-6998 [email protected] -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Martin Packer Sent: Wednesday, October 31, 2012 5:25 AM To: [email protected] Subject: Re: DASD and Cache Fast Write & DS8800/DS8700 An interesting question, Ken. Don't know about the settings but 2 observations: I very rarely see significant USAGE of CFW in data - but it might be enabled. I always see significant Cached Writes (a la DFW) in data - sometimes as much as 50% of cached reads. But I couldn't tell you if it's possible to disable it. So, given your motivation was to check your controllers are set up properly in these 2 regards they almost certainly are. And I'd use RMF Cache Activity Report / SMF 74-5 (and other records and downstream tooling) to check how they're doing. A question in return to IBM-MAIN: Is it possible to set the size of the DFW portion of the cache? Used to be called NVS size but that's such an old term it's probably not used anymore when it comes to actual machine configuration. Cheers, Martin Martin Packer, zChampion, Principal Systems Investigator, Worldwide Banking Center of Excellence, IBM +44-7802-245-584 email: [email protected] Twitter / Facebook IDs: MartinPacker Blog: https://www.ibm.com/developerworks/mydeveloperworks/blogs/MartinPacker From: Ken Leidner <[email protected]> To: [email protected], Date: 10/31/2012 02:55 AM Subject: DASD and Cache Fast Write & DS8800/DS8700 Sent by: IBM Mainframe Discussion List <[email protected]> Does setting the DASD FW or Cache FW on or off still exist on the DS8800/DS8700 devices. I know when they first came out for a 3990-6 controller, the performance different was night and day. But on the newer devices isn't it always on? Can I really still turn it off? Do I still need to check to make sure it is on? Ken Leidner [email protected] ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] 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 [email protected] with the message: INFO IBM-MAIN This e-mail, including attachments, may include confidential and/or proprietary information, and may be used only by the person or entity to which it is addressed. If the reader of this e-mail is not the intended recipient or his or her authorized agent, the reader is hereby notified that any dissemination, distribution or copying of this e-mail is prohibited. If you have received this e-mail in error, please notify the sender by replying to this message and delete this e-mail immediately. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
