Having done all of this, I would suggest that you start with EXCP and then progress to EXPC/VR. Even with EXCP you have to know and understand the relationship of the CCW's you are going to use. Read carefully. Start simple. Build on it slowly.
Going from EXCP to EXCP/VR is a big jump. Everything you have to do for EXCP/VR you will have to do for STARTIO, plus more. Once you have EXCP/VR running, go look at the STARTIO macro in SYS1.MODGEN. EXCP and EXCP/VR have some guard rails built into them, but you can still really screw things up at EXCP/VR because you will have to supply the REAL addresses for the CCW's. When, and if, you start playing with EXCP/VR, I strongly suggest using a sandbox LPAR. If you ever get to STARTIO that suggestion should rise to a requirement. Chris Blaicher Technical Architect Syncsort, Inc. -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Mike Myers Sent: Saturday, February 8, 2020 4:07 PM To: [email protected] Subject: Re: Startio documentation [ External - This message originated Externally. Use proper judgment and caution with attachments, links, or responses. ] Hey Eric: You might want to start your exploration at a higher level than the lowest level you can possibly go to understand the internals of z/OS I/O. For example you might want to look at EXCP or EXCPVR first, as both prepare for entry into IOS, but both do special setup functions to make that possible. As an example of the setup needed, consider the difference between EXCP and EXCPVR. EXCP, among other preliminary things, converts all addresses in the channel program CCWs being passed to IOS from virtual to real addresses. Ultimately, these areas must be pagefixed so as to remain in storage during the actual I/O operation. Since STARTIO comes at the next lower level, everything that an access method must do before calling EXCP must also be done. This includes creating a DCB, an IOSB, etc. I would recommend you start here, if you haven't already. as it covers EXCP and EXCPVR. https://www.ibm.com/support/knowledgecenter/SSLTBW_2.1.0/com.ibm.zos.v2r1.idas300/eyocp.htm Mike Myers On 2/8/20 12:48 PM, Erik Janssen wrote: > Hello List, > > Out of curiosity I want to learn a bit more about startio. Don't > worry, I won't go and attempt to mess up someones z/os lpar, it is > just for pure nerd brain entertainment. Searching through the archives > I found that there is a whitepaper that was written by Peter Haas > called "The STARTIO Facility of MVS", that there were some examples > called startio.txt or startio.ex.txt, that Bill Fairchild gave a SHARE > presentation on the subject in March 2009 in Austin and that IBM > documented it, partially, in IOS logic manuals; the versions for > OS/VS2 R2 through R3.8 were publicly available. > > My search engines efforts to find any of the mentioned documents have failed > so far, so is there anybody on the list that has (some of) the mentioned > documents available and is willing to share? > > Kind regards, > > Erik Janssen. > PS. I had posted the same question through Google groups, but that doesn't > work in a way that the actual list gets the message it seems. > > ---------------------------------------------------------------------- > 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 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
