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IDS Forum
Re: Someone have a technique to alter tables w....
Posted By: Fernando Nunes
Date: Wednesday, 2 May 2012, at 6:00 p.m.
In Response To: Re: Someone have a technique to alter tables w.... (Cesar Inacio Martins)
Cesar:
Both PMRs refer only to a CREATE INDEX ONLINE. The APAR opened for the
documentation refers only to that. The feature request created also refers
only to that.
Is there any other situation where you've seen this behavior?
1- I noticed once you tried to kill all the sessions that were using the
table, as shown by "onstat -g opn". This will not show all the relevant
tables. I can get you a better script.
2- You mention a process where you set IFX_DIRTY_WAIT, lock the systable's
record etc... This looks like something we do to ALTER TABLE (I documented
it in a very old blog post). I suppose you don't do that to create an index
online... So, again, is the ONLINE index the only situation? If it isn't,
the documentation change and feature request looks insufficient to cover
all the scenarios....
3- Accordingly to the PMR, the dirty entries in the dictionary cache may be
related. At first glance it feels odd... (if there are multiple dirty
entries and one clean entry, why not use the clean?). But this is way out
of my league... maybe Marco can help
I was trying to reproduce it and I managed to get -710. But it went away
without even closing the session... but I believe I'm still far from a
reproduction... I will continue to look into this as time permits.
On Wed, May 2, 2012 at 7:36 PM, Cesar Inacio Martins <
cesar_inacio_martins@yahoo.com.br> wrote:
> Hi Art,
>
> > The statement cache, when I open the first PMR it was disabled because
> > of other problem with it (STMT_CACHE = 1 ), we enable it (STMT_CACHE =2
> > ) when we update to FC9 or FC9X6 (I don't remember with sure what of
> both).
> > Honestly I don't remember if I try flush the stat_cache.
>
> On 2/5/2012 15:10, Art Kagel wrote:
> > You are correct, the -710 should not affect new sessions. I noticed on
> one
> > post that you have statement caching turned on. What happens if you
> > disable the statement cache? That is probably where the invalid query
> > plans are being stored and reused by the new applications with nearly
> > identical statements to run.
> >
> > Art
> >
> > Art S. Kagel
> > Advanced DataTools (www.advancedatatools.com)
> > Blog: http://informix-myview.blogspot.com/
> >
> > Disclaimer: Please keep in mind that my own opinions are my own opinions
> > and do not reflect on my employer, Advanced DataTools, the IIUG, nor any
> > other organization with which I am associated either explicitly,
> > implicitly, or by inference. Neither do those opinions reflect those of
> > other individuals affiliated with any entity with which I am affiliated
> nor
> > those of the entities themselves.
> >
> > On Wed, May 2, 2012 at 1:49 PM, Cesar Inacio Martins<
> > cesar_inacio_martins@yahoo.com.br> wrote:
> >
> >> Hi Art,
> >>
> >> Considering the application is closed when reach -710 (the session with
> >> informix is closed) the PID of 4GL die...
> >> When the user start the application again, the problem should persists?
> >> Since when the application was restarted, naturally all prepared
> >> statements will be re-executed, so... this isn't enough? (for this user
> >> in particular)
> >>
> >> Here, the way what the code is structured, isn't viable include now a
> >> code to handle this and I not sure if will work since the behave what I
> >> describe before occur today (new sessions get -710)...
> >>
> >> On 2/5/2012 12:48, Art Kagel wrote:
> >>> If the AUTO_REPREPARE is not solving the situation, then you will have
> to
> >>> recode your applications to handle the error by repreparing etc. All of
> >>> the application and middleware code I wrote at Bloomberg years ago was
> >>> coded to do that because prior to version 11.10 this was a much bigger
> >>> problem. Most -710 errors are internally handled by the engine now, but
> >>> there are still some, like this one of altering a parent table in a
> >> foreign
> >>> key relationship, that still can crop up.
> >>>
> >>> Art
> >>>
> >>> Art S. Kagel
> >>> Advanced DataTools (www.advancedatatools.com)
> >>> Blog: http://informix-myview.blogspot.com/
> >>>
> >>> Disclaimer: Please keep in mind that my own opinions are my own
> opinions
> >>> and do not reflect on my employer, Advanced DataTools, the IIUG, nor
> any
> >>> other organization with which I am associated either explicitly,
> >>> implicitly, or by inference. Neither do those opinions reflect those of
> >>> other individuals affiliated with any entity with which I am affiliated
> >> nor
> >>> those of the entities themselves.
> >>>
> >>> On Wed, May 2, 2012 at 11:24 AM, Cesar Inacio Martins<
> >>> cesar_inacio_martins@yahoo.com.br> wrote:
> >>>
> >>>> Hi Art.
> >>>> The database always have the AUTO_REPREPARE active.
> >>>> onstat -c |grep ^AUTO_RE
> >>>> AUTO_REPREPARE 1
> >>>>
> >>>> But we don't try force it thru user environment AUTO_REPREPARE=1 ...
> >>>> should ?
> >>>>
> >>>> No Stored procedures are used at this situation, any way we was tried
> >>>> update statistics for procedure too..
> >>>>
> >>>> On 2/5/2012 12:01, Art Kagel wrote:
> >>>>> Prior to 11.50 you could only handle this in your code by adding a
> >>>>> test in your applications after the execution of a prepared statement
> >>>>> or the opening of a cursor against a prepared statement so that if
> the
> >>>>> operation returns SQLCODE == -710 then reprepare the statement and
> >>>>> reexecute the statement or redeclare and reopen the cursor and all
> >>>>> would be well. There is now another way:
> >>>>>
> >>>>> You can try setting the ONCONFIG parameter or the environment
> variable
> >>>>> AUTO_REPREPARE to '1' which tells the engine to automatically
> >>>>> reprepare any prepared statement or recompile any stored procedure
> >>>>> that encounters a -710 error
> >>>>>
> >>>>> Art
> >>>>>
> >>>>> Art S. Kagel
> >>>>> Advanced DataTools (www.advancedatatools.com
> >>>>> <http://www.advancedatatools.com>)
> >>>>> Blog: http://informix-myview.blogspot.com/
> >>>>>
> >>>>> Disclaimer: Please keep in mind that my own opinions are my own
> >>>>> opinions and do not reflect on my employer, Advanced DataTools, the
> >>>>> IIUG, nor any other organization with which I am associated either
> >>>>> explicitly, implicitly, or by inference. Neither do those opinions
> >>>>> reflect those of other individuals affiliated with any entity with
> >>>>> which I am affiliated nor those of the entities themselves.
> >>>>>
> >>>>>
> >>>>>
> >>>>> On Wed, May 2, 2012 at 9:37 AM, Cesar Inacio Martins
> >>>>> <cesar_inacio_martins@yahoo.com.br
> >>>>> <mailto:cesar_inacio_martins@yahoo.com.br>> wrote:
> >>>>>
> >>>>> Hi,
> >>>>>
> >>>>> 11.50 FC9X6 , AIX 6.1
> >>>>>
> >>>>> We suffer with one situation at our production where just not
> >>>>> found a acceptable way to work yet...
> >>>>> I already open a PMR (for me this is a defect) but for IBM support
> >>>>> is just "work as design" .... so, no solution...
> >>>>> Just a correction / better documentation was made.
> >>>>>
> >>>>>
> >>>>> THE PROBLEM
> >>>>> - When I alter one table (any changes cited bellow), no matter if
> >>>>> I get the exclusive lock for this table and all others what exists
> >>>>> any FK from/to it... new users sessions, when try
> >>>>> update/insert/delete any for this references tables get the error
> >>>>> -710 Table<table-name> has been dropped, altered, or renamed.
> >>>>> - create/drop index online/offline OR add/drop trigger OR
> >>>>> add/modify/drop column OR alter any constraint...
> >>>>>
> >>>>>
> >>>>> TODAY, THE UNIQUE SOLUTION WHEN THIS OCCUR:
> >>>>> - Stop all our production, kill all users (put the instance in
> >>>>> quiescent) and back online immediately .
> >>>>>
> >>>>>
> >>>>>
> >>>>> HOW I PROCEED WHEN NEED TO CHANGE SOME TABLE:
> >>>>> - set IFX_DIRTY_WAIT
> >>>>> - open dbaccess , start new transaction (begin work)
> >>>>> - lock table in exclusive mode
> >>>>> - grant a dummy select over the table (lock sys*)
> >>>>> - At other session, kill all users what is accessing this table
> >>>>> (identifying with onstat -g opn + onmode -z)
> >>>>> - execute the alter over the table
> >>>>> - commit
> >>>>> If the table have any FK from/to it , I lock and kill users for
> >>>>> this tables too.
> >>>>> But, at 90% of the situations , after all executed successfully ,
> >>>>> the system stuck with -710 error.
> >>>>> Do not matter if the user close all application and open a new
> >>>>> session, the error -710 persist.
> >>>>>
> >>>>>
> >>>>> THE ENVIRONMENT
> >>>>> - IFX 11.50 FC9X6 , AIX 6.1 , 4GL 7.32
> >>>>> - Is a centralized 24x7 system what control all plants of the
> >>>>> company .
> >>>>> - Avg of 1800 sessions concurrent at high peak time and 400
> >>>>> sessions at lower peak time.
> >>>>> - User sessions: 70% incoming from 4GL system (most important and
> >>>>> where suffer with the problem)
> >>>>> - User sessions: 25% incoming from Web/Java system
> >>>>> - User sessions: 5% others....
> >>>>> - Database have AUTO_REPREPARE and STMT_CACHE active
> >>>>> - The isolation used is 99% 'dirty read' .
> >>>>> - The 4GL system work mostly with prepared SQLs where they prepare
> >>>>> at beginner of 4GL connection then keep this prepare active during
> >>>>> they execution.
> >>>>>
> >>>>>
> >>>>>
> >>>>> CONSIDERATIONS
> >>>>> - If check with onstat -g dic , always have a refcnt and dirty
> >>>>> over the tables involved. This before , during and after the alter
> >>>>> . Even during the alter, consider the table in exclusive lock +
> >>>>> lock over sys* (grant select).
> >>>>> - After the alter, appear new references on onstat -g dic. (with
> >>>>> dirty and without dirty)
> >>>>> - After finish all alters, if the user got erro -710, close all
> >>>>> system , open it again e try again, they stuck at -710 again and
> >>>>> again and again and again....
> >>>>> - I try simulate the problem, but with few users, this behave do
> >>>>> not occur.
> >>>>> - Bellow is a stack trace (trapped with onmode -I 710) when the
> >>>>> user tryed insert a register over a table where is relationed with
> >>>>> the table altered (in this case, added a new index online over
> >>>>> columns what not involve the FK)
> >>>>>
> >>>>> 0x00000001000b76a8 (oninit)afstack
> >>>>> 0x00000001000b97bc (oninit)afhandler
> >>>>> 0x0000000100130b90 (oninit)check_traperror
> >>>>> 0x00000001001faa94 (oninit)sqerr
> >>>>> 0x00000001001fa550 (oninit)sqerr1
> >>>>> 0x00000001001f9e54 (oninit)sqnameerr
> >>>>> 0x000000010066e4dc (oninit)chkmajvers
> >>>>> 0x000000010066eb24 (oninit)openrel
> >>>>> 0x00000001006523b4 (oninit)chkparent
> >>>>> 0x000000010065b2d0 (oninit)chkrowcons
> >>>>> 0x0000000100782790 (oninit)addone
> >>>>> 0x0000000100784e10 (oninit)insone_next
> >>>>> 0x0000000100769994 (oninit)doinsert
> >>>>> 0x000000010041cff8 (oninit)aud_doinsert
> >>>>> 0x00000001004259f8 (oninit)excommand
> >>>>> 0x000000010044b3bc (oninit)sq_execute
> >>>>> 0x000000010022463c (oninit)sqmain
> >>>>> 0x000000010037c160 (oninit)listen_verify
> >>>>> 0x000000010037a608 (oninit)spawn_thread
> >>>>> 0x0000000100dd528c (oninit)startup
> >>>>>
> >>>>>
> >>>>>
> >>>>> At my point of view, Informix isn't able to work 100% online if
> >>>>> you need to change your scheme (add a simple index using online
> >>>>> mode) when you use referential integrity.
> >>>>> I believed this is because our method of work (prepare at start of
> >>>>> application, and keep this prepared active to reuse it), anyway,
> >>>>> should we suffer with this consequences!???
> >>>>>
> >>>>> Is there some technique to alter a table what I miss here ?
> >>>>>
> >>>>> Cesar
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> _______________________________________________
> >>>>> Informix-list mailing list
> >>>>> Informix-list@iiug.org<mailto:Informix-list@iiug.org>
> >>>>> http://www.iiug.org/mailman/listinfo/informix-list
> >>>>>
> >>>>>
> >>>>
> >>>>
> >>
> >
>
> *******************************************************************************
> >>>> Forum Note: Use "Reply" to post a response in the discussion forum.
> >>>>
> >>>>
> >>> --14dae9340d59e9b88604bf0f9d2d
> >>>
> >>>
> >>>
> >>
> >
>
> *******************************************************************************
> >>> Forum Note: Use "Reply" to post a response in the discussion forum.
> >>>
> >>
> >>
> >>
> >
>
> *******************************************************************************
> >> Forum Note: Use "Reply" to post a response in the discussion forum.
> >>
> >>
> > --14dae9340c0155700404bf1199de
> >
> >
> >
>
> *******************************************************************************
> > Forum Note: Use "Reply" to post a response in the discussion forum.
> >
>
>
>
> *******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>
--
Fernando Nunes
Portugal
http://informix-technology.blogspot.com
My email works... but I don't check it frequently...
--20cf3074b01e11c30004bf14d1fb
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