[DB2-L] LPL and indoubt

Philip Sevetson

[DB2-L] LPL and indoubt
Mike, for the convenience of those for whom long URL's don't work (good thought, that) I have created a TinyURL reference for the webpage:
http://tinyurl.com/2e2tdp
Or the preview TinyURL:
http://preview.tinyurl.com/2e2tdp

--Phil Sevetson, NYCAPS DBA Support
Financial Information Services Agency of The City of New York
450 West 33rd Street, 4th Floor
New York, NY 10001
phone: (212) 857-1688
mailto: [login to unmask email]
________________________________________
From: DB2 Data Base Discussion List [mailto:[login to unmask email] On Behalf Of Vaughan, Mike
Sent: Wednesday, December 05, 2007 11:08 AM
To: [login to unmask email]
Subject: Re: [DB2-L] LPL and indoubt

The following link is probably a better reference -- http://publib.boulder.ibm.com/cgi-bin/bookmgr/BOOKS/dfht2p07/1.2.2.4?ACTION=MATCHES&REQUEST=in-doubt&TYPE=FUZZY&SHELF=dfhpushc.bks&DT=20100721122456&CASE=&searchTopic=TOPIC&searchText=TEXT&searchIndex=INDEX&rank=RANK&ScrollTOP=FIRSTHIT#FIRSTHIT. 
 
   Knowing that link most likely will not come across correctly, it points to the "CICS Recovery and Restart Guide", section titled "Resynchronization after system or connection failure" and the specific quote I am looking at states "Resynchronization takes place automatically when communications are next established between subordinate and coordinator. Any decisions held by the coordinator are passed to the subordinate, and in-doubt units of work complete normally".  Now obviously this is specific to CICS so maybe the difference in opinions is coming from the perspective of different commit coordinators.  I do know we were (finally) able to get this same behavior after a websphere failure, although it took awhile for us to get things setup correctly to make it work.  

________________________________________
From: Vaughan, Mike
Sent: Wednesday, December 05, 2007 9:40 AM
To: 'DB2 Database Discussion list at IDUG'
Subject: RE: [DB2-L] LPL and indoubt
   I'm pretty confident on this one since we see it happen pretty frequently (well, ok, not "frequently", but often enough).  One manual reference to point to from just a real quick search would be the command reference under "recover indoubt" -- "This command should only be used when automatic resolution will not work". 

________________________________________
From: DB2 Data Base Discussion List [mailto:[login to unmask email] On Behalf Of Nicola Nur
Sent: Wednesday, December 05, 2007 9:29 AM
To: [login to unmask email]
Subject: Re: [DB2-L] LPL and indoubt
Thanks Mike
I am not sure if what you are saying is correct that is why I asked the question originally. I heard two arguments. One point of view says that indoubt threads cannot be resolved automatically and needs manual intervention (this is the view I subscribe to ) and the other point of view is like yours as you explained it.
 
Can we hear from somebody else in that regard please?
 
thanks

"Vaughan, Mike" <[login to unmask email]> wrote:
One clarification on automatic recovery of in-doubt threads -- these
will be automatically resolved as long as the resource manager causing
the in-doubt situation comes back up. An in-doubt thread just means we
got half-way through a 2-phase commit scenario and one of the resource
managers went away - for example, a CICS region crashes while a
transaction is in the process of a commit/syncpoint. When that region
comes back up and reconnects to DB2 one of the things that will happen
is resolution of the in-doubt threads. Of course, if the region is
brough up with a cold-start then the resolution will not happen and the
commands need to be issued.

-----Original Message-----
From: DB2 Data Base Discussion List [mailto:[login to unmask email] On
Behalf Of Mike Bell
Sent: Tuesday, December 04, 2007 3:58 PM
To: [login to unmask email]
Subject: Re: [DB2-L] LPL and indoubt

LPL and in-doubt are two different things.

In-doubt is never automatically recovered by DB2. You have to issue the
command. And if you find a 2 day old in-doubt thread and tell DB2 to
abort it, DB2 will be scanning archive logs for a long long time.

LPL may be automatically recovered - see the manual about automatic LPL
recovery. If that fails for any of the reasons listed in messages and
codes then you get to do RECOVER or START DATABASE to restart the LPL
recovery.
LPL is basically an IO error that DB2 detects and corrects. There are
flags in the page that DB2 knows should match a specific way and if they
don't the page (pages) get added to the LPL list. Something I didn't
notice before but the V8 manual explains that now only the pages in the
LPL are locked not the entire tablespace during LPL recovery.

I might be able to construct a scenario where you could combine in-doubt
and LPL but can't think of one off the top of my head.

Mike
HLS Technologies

-----Original Message-----
From: DB2 Data Base Discussion List [mailto:[login to unmask email] On
Behalf Of Nick
Sent: Tuesday, December 04, 2007 2:32 PM
To: [login to unmask email]
Subject: [DB2-L] LPL and indoubt

Hi colleagues
Our db2 is z/os v8.1.
I know what LPL is and how to display the pages in LPL status.
I know what indoubt threads are and what actions need to recover them or
abort them.
A colleague of mine pointed out to me that db2 will do the action on
indoubt threads automatically and said that the action is the LPL action. My
take on it that LPL and indoubt threads are two different issues and are
not correlated; and that indoubt threads need manual intervention to be
cleared.
Am i wrong or missing the point? or is there really a connection between
the pages in the LPL and the indoubt threads? Is the action of db2 to
recover the LPL pages a result of an effort to clear the indoubt
threads?

appreciate your help and comment.

thanks in advance

Nick Nur


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Mike Turner

Re: LPL and indoubt
(in response to Philip Sevetson)
Mike is correct. For example, if the in-doubt thread is a CICS thread it
will be resolved automatically by DB2 and the CICS region when the CICS
region comes back up, unless CICS is cold started in which case both CICS
and DB2 will report that they cannot resolve the in-doubt status. The same
is true for IMS. For distributed threads the thread should be resolved
automatically when the connection is re-established so long as the client
end is smart enough. If the client is another DB2 for z/OS, then it IS smart
enough.

Regards
Mike Turner
Email: [login to unmask email]
Tel: +44 (0)1565 873702
web: www.michael-turner.ltd.uk
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-----Original Message-----
From: [login to unmask email] [mailto:[login to unmask email]On
Behalf Of Vaughan, Mike
Sent: Wednesday, 05 December 2007 15:40
To: [login to unmask email]
Subject: Re: [DB2-L] LPL and indoubt


I'm pretty confident on this one since we see it happen pretty frequently
(well, ok, not "frequently", but often enough). One manual reference to
point to from just a real quick search would be the command reference under
"recover indoubt" -- "This command should only be used when automatic
resolution will not work".




From: DB2 Data Base Discussion List [mailto:[login to unmask email] On Behalf
Of Nicola Nur
Sent: Wednesday, December 05, 2007 9:29 AM
To: [login to unmask email]
Subject: Re: [DB2-L] LPL and indoubt


Thanks Mike
I am not sure if what you are saying is correct that is why I asked the
question originally. I heard two arguments. One point of view says that
indoubt threads cannot be resolved automatically and needs manual
intervention (this is the view I subscribe to ) and the other point of view
is like yours as you explained it.

Can we hear from somebody else in that regard please?

thanks

"Vaughan, Mike" <[login to unmask email]> wrote:
One clarification on automatic recovery of in-doubt threads -- these
will be automatically resolved as long as the resource manager causing
the in-doubt situation comes back up. An in-doubt thread just means we
got half-way through a 2-phase commit scenario and one of the resource
managers went away - for example, a CICS region crashes while a
transaction is in the process of a commit/syncpoint. When that region
comes back up and reconnects to DB2 one of the things that will happen
is resolution of the in-doubt threads. Of course, if the region is
brough up with a cold-start then the resolution will not happen and the
commands need to be issued.

-----Original Message-----
From: DB2 Data Base Discussion List [mailto:[login to unmask email] On
Behalf Of Mike Bell
Sent: Tuesday, December 04, 2007 3:58 PM
To: [login to unmask email]
Subject: Re: [DB2-L] LPL and indoubt

LPL and in-doubt are two different things.

In-doubt is never automatically recovered by DB2. You have to issue the
command. And if you find a 2 day old in-doubt thread and tell DB2 to
abort it, DB2 will be scanning archive logs for a long long time.

LPL may be automatically recovered - see the manual about automatic LPL
recovery. If that fails for any of the reasons listed in messages and
codes then you get to do RECOVER or START DATABASE to restart the LPL
recovery.
LPL is basically an IO error that DB2 detects and corrects. There are
flags in the page that DB2 knows should match a specific way and if they
don't the page (pages) get added to the LPL list. Something I didn't
notice before but the V8 manual explains that now only the pages in the
LPL are locked not the entire tablespace during LPL recovery.

I might be able to construct a scenario where you could combine in-doubt
and LPL but can't think of one off the top of my head.

Mike
HLS Technologies

-----Original Message-----
From: DB2 Data Base Discussion List [mailto:[login to unmask email] On
Behalf Of Nick
Sent: Tuesday, December 04, 2007 2:32 PM
To: [login to unmask email]
Subject: [DB2-L] LPL and indoubt

Hi colleagues
Our db2 is z/os v8.1.
I know what LPL is and how to display the pages in LPL status.
I know what indoubt threads are and what actions need to recover them or
abort them.
A colleague of mine pointed out to me that db2 will do the action on
indoubt

threads automatically and said that the action is the LPL action. My
take on it that LPL and indoubt threads are two different issues and are
not correlated; and that indoubt threads need manual intervention to be
cleared.
Am i wrong or missing the point? or is there really a connection between
the

pages in the LPL and the indoubt threads? Is the action of db2 to
recover the LPL pages a result of an effort to clear the indoubt
threads?

appreciate your help and comment.

thanks in advance

Nick Nur



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at http://www.idug.org
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home page at http://www.idugdb2-l.org/archives/db2-l.html. From that page
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IMPORTANT NOTICE:

IDUG is pleased to announce a series of upgrades to the DB2-L discussion listserv that are being implemented to improve reliability and the overall user experience of DB2-L. These changes are coming on November 30th. Details at http://www.idug.org

---------------------------------------------------------------------------------
Welcome to the IDUG DB2-L list. To unsubscribe, go to the archives and home page at http://www.idugdb2-l.org/archives/db2-l.html. From that page select "Join or Leave the list". The IDUG DB2-L FAQ is at http://www.idugdb2-l.org. The IDUG List Admins can be reached at [login to unmask email] Find out the latest on IDUG conferences at http://conferences.idug.org/index.cfm

Raymond Bell

Re: FW: [DB2-L] LPL and indoubt
(in response to Mike Turner)
Phil,

Well, how cool is that? Just visited the 'Tiny URL' website - what a
good idea. Thanks for the tip!

Cheers,


Raymond

-----Original Message-----
From: DB2 Data Base Discussion List [mailto:[login to unmask email] On
Behalf Of Sevetson, Phil
Sent: 05 December 2007 16:23
To: [login to unmask email]
Subject: [DB2-L] FW: [DB2-L] LPL and indoubt

Mike, for the convenience of those for whom long URL's don't work (good
thought, that) I have created a TinyURL reference for the webpage:
http://tinyurl.com/2e2tdp
Or the preview TinyURL:
http://preview.tinyurl.com/2e2tdp

--Phil Sevetson, NYCAPS DBA Support
Financial Information Services Agency of The City of New York
450 West 33rd Street, 4th Floor
New York, NY 10001
phone: (212) 857-1688
mailto: [login to unmask email]

IMPORTANT NOTICE:

IDUG is pleased to announce a series of upgrades to the DB2-L discussion listserv that are being implemented to improve reliability and the overall user experience of DB2-L. These changes are coming on November 30th. Details at http://www.idug.org

---------------------------------------------------------------------------------
Welcome to the IDUG DB2-L list. To unsubscribe, go to the archives and home page at http://www.idugdb2-l.org/archives/db2-l.html. From that page select "Join or Leave the list". The IDUG DB2-L FAQ is at http://www.idugdb2-l.org. The IDUG List Admins can be reached at [login to unmask email] Find out the latest on IDUG conferences at http://conferences.idug.org/index.cfm