IDS Forum

Someone have a technique to alter tables with FK ?

Posted By: Cesar Inacio Martins
Date: Wednesday, 2 May 2012, at 9:38 a.m.

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

Messages In This Thread

• Someone have a technique to alter tables with FK ?
  Cesar Inacio Martins -- Wednesday, 2 May 2012, at 9:38 a.m.
  • Re: Someone have a technique to alter tables with
    Fernando Nunes -- Wednesday, 2 May 2012, at 11:26 a.m.
    • Re: Someone have a technique to alter tables w....
      Fernando Nunes -- Wednesday, 2 May 2012, at 11:31 a.m.
      • Re: Someone have a technique to alter tables w....
        Cesar Inacio Martins -- Wednesday, 2 May 2012, at 1:49 p.m.
    • Re: Someone have a technique to alter tables w....
      Cesar Inacio Martins -- Wednesday, 2 May 2012, at 11:59 a.m.

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