Erik:
I took the reference I passed you earlier a bit further. If you look
here, you will find a lot more detail on EXCP, EXCPVR and STARTIO. It's
been a long time since I did my own channel programming and made use of
EXCP, but I think you will find all you need to know here. You will also
have to look into the structure of channel programming and CCWs for
specific device types to understand more about what is really happening.
The Principles of Operation can supply much of this.
https://www.ibm.com/support/knowledgecenter/SSLTBW_2.1.0/com.ibm.zos.v2r1.idas300/eyocp.htm
Mike Myers
On 2/8/20 10:26 PM, Susan Shumway wrote:
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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