I tried to do something like that around 1985. At the time I was using EXCP in an authorized program to do most of the same things that STARTIO will allow you to do but unauthorized EXCP will not, such as do I/O to an offline device, do I/O to an unallocated DASD track, etc. The way I was doing it with EXCP was to modify the DEB after an OPEN so that the DEB's UCB pointer contained the address of whatever device I really wanted to access, the DEB's extent list contained the CCHH of whatever track I wanted to access, etc. I wanted to be able to use different caching algorithms as well, but there was no way to do that with the fields in the 1985 version of the DEB. I raised the issue in a SHARE project, but it did not rise to the level of a requirement. Within a year or two IBM had added many new fields into the DEB Extension that answered most of my needs. But by then I was using STARTIO anyway, so I quit trying to do everything via EXCP. There are still quite a few in! teresting things that can be done only with STARTIO; e.g., direct the I/O to a specific channel path if the device has more than one path available, use MIDAW and several other indirect addressing formats, use Transport Mode, increase the scheduling and/or execution priority of your I/O request to way above everybody else's, and exploit almost every I/O feature documented in the PoO.
The STARTIO interface is quite dangerous to the health of the system if it is not used correctly, which may also be part of why IBM has never officially externally documented the interface. They did release some working examples of it, however, back in the ancient days when source code for JES3, Media Manager, and other strategic components was available. They also documented how STARTIO works internally fairly well in the days of MVS/XA in their 17-volume logic library, but did not include a working sample of how to invoke it. Bill Fairchild Rocket Software -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@bama.ua.edu] On Behalf Of Shmuel Metz (Seymour J.) Sent: Monday, June 20, 2011 9:11 AM To: IBM-MAIN@bama.ua.edu Subject: Re: Some tests with MFNetDisk PRO In <BANLkTinDfr1-b=b5o-of0x4cznzjmmz...@mail.gmail.com>, on 06/19/2011 at 11:42 AM, shai hess <shai.h...@gmail.com> said: >I do not understand why there is no example of startio. IBM doesn't want to support customer use of STARTIO. IBM doesn't want to document the available drivers. I suspect that it is a resources issue rather than an IP issue, Is there a Share requirement to open up the interface? -- Shmuel (Seymour J.) Metz, SysProg and JOAT ISO position; see <http://patriot.net/~shmuel/resume/brief.html> We don't care. We don't have to care, we're Congress. (S877: The Shut up and Eat Your spam act of 2003) ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
