>Apparently you can deactivate DSF for one device by using the Force Deactivate >function. I meant to type DFW instead of DSF. And DFW means Dasd Fast Write and not the abbreviation for the Dallas-Ft. Worth airport. :-)
Bill Fairchild Programmer Rocket Software 408 Chamberlain Park Lane * Franklin, TN 37069-2526 * USA t: +1.617.614.4503 * e: [email protected] * w: www.rocketsoftware.com -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Bill Fairchild Sent: Thursday, November 01, 2012 8:58 AM To: [email protected] Subject: Re: DASD and Cache Fast Write & DS8800/DS8700 The IBM 2105 Command Reference book (SC26-7298-01; June 2000) says this about the bit in the Define Extent parameters that would inhibit (disable) DASD Fast Write for that one channel program: "This bit is ignored by ESS." So DFW is always used by all I/O requests to a specific device if it is enabled at the device level for that one device. The same book says this about the Set Subsystem Mode command, which would turn DFW on or off at the device level: Activate DASD Fast Write for Addressed Device. Accepted and ignored by ESS. Deactivate DASD Fast Write for Addressed Device. Accepted and ignored by ESS. Force Deactivate DASD Fast Write for Addressed Device. Apparently you can deactivate DSF for one device by using the Force Deactivate function. I have never tried to do this. The same book indicates that Cache Fast Write can be disabled for the entire subsystem but not for an individual device. If allowed at the subsystem level, it can optionally be used by any one I/O request by setting certain data in the Define Extent parameters. Bill Fairchild Programmer Rocket Software 408 Chamberlain Park Lane * Franklin, TN 37069-2526 * USA t: +1.617.614.4503 * e: [email protected] * w: www.rocketsoftware.com -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Ron Hawkins Sent: Thursday, November 01, 2012 7:59 AM To: [email protected] Subject: Re: DASD and Cache Fast Write & DS8800/DS8700 >I believe that DFW cannot be turned off on 2105 and 2107 emulation. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
