Hi Erik,
I searched the Technical help database for System z (
https://www14.software.ibm.com/webapp/set2/psearch/search?domain=sysz )
and got plenty of hits for "startio", but none with the term in the
title. If you haven't looked there yet, give it a try and see if
anything looks helpful.
There are also a number of hits to the term in the V2R4 KC, though
probably not true nerd brain entertainment fodder like what you're
looking for:
https://www.ibm.com/support/knowledgecenter/search/startio?scope=SSLTBW_2.4.0
. Since it's just a simple term search, Mike's recommended KC reading is
most likely your better bet.
-Sue Shumway
On 2/8/2020 7:11 PM, Christopher Y. Blaicher wrote:
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.
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Sue Shumway
z/OS Project Lead and Client Advocate
IBM Poughkeepsie
[email protected]
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