IDS Forum

Re: Unique problem

Posted By: Sushil Shirodkar
Date: Friday, 2 April 2004, at 8:41 a.m.

In Response To: Unique problem (Sushil Shirodkar)

Hi Jonathan,

Thanks for the response, good idea to trace the problem. It looks like we
found the problem let me monitor for 3/4 days and I will update the details
about it.
The problem is in the apps.

Thanks
Sushil....


>From: Jonathan Leffler <jleffler@us.ibm.com>
>To: "Sushil Shir...." <sushilps@hotmail.com>
>CC: forum.subscriber@iiug.org, ids@iiug.org
>Subject: Re: Unique problem [2778]
>Date: Thu, 1 Apr 2004 15:22:40 -0800
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>
>This could be a classic TOCTOU - time of check, time of use - problem.
>Unless you have your database rigged to prevent, you can have two
>processes, A and B, that do:
>A: check the non-existence
>B: check the non-existence of the number
>A: increment and insert and commit.
>B: increment and insert *fails* because the number it read is no longer
>unique.
>
>You have different options - I note you're using HDR. You can upgrade to
>9.40 and use SEQUENCES instead. Or you can use a SERIAL column (insert a
>placeholder record - then update things appropriately).
>
>...oh...you don't have source code. That's going to make life
>interesting. I guess you are left with export SQLIDEBUG=2:my_trace and
>then run the program. It should create a binary file my_trace_12345 for
>some process ID, and ship that off to IBM Tech Support. That's about all
>that you can do without modifying the app. Next time, remember to ask
>them for the explicit instructions - they may have something else in mind,
>but I don't know what.
>
>
>--
>Jonathan Leffler (jleffler@us.ibm.com)
>STSM, Informix Database Engineering, IBM Data Management
>4100 Bohannon Drive, Menlo Park, CA 94025
>Tel: +1 650-926-6921 Tie-Line: 630-6921
> "I don't suffer from insanity; I enjoy every minute of it!"
>
>
>
>forum.subscriber@iiug.org wrote on 04/01/2004 12:14:37 PM:
>
> > Hello Everybody,
> >
> > Env: 9.30 uc3 AIX 5.1 having HDR. Appl: VB 6. ODBC 2.81
> >
> > We have a reservation table with UNIQUE key on resnumber, program
>generates
> > some random number and checks in the table if that number exist. Program
>
> > doesn't get the response back and assumes that the number doesn't exist
>and
> > when it inserts into the table it fails because the number already exist
>in
> > the table.
> >
> > I am not able to figure out, how this is taking place, have been talking
>to
> > IBM and they have asked to open the trace log at ODBC level. Any ideas
>?
> >
> > BTW. the software is outsourced we don't have any source-code in house.
>
>

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Messages In This Thread

• Unique problem
  Sushil Shirodkar -- Thursday, 1 April 2004, at 3:14 p.m.
  • Re: Unique problem
    Jonathan Leffler -- Thursday, 1 April 2004, at 6:26 p.m.
  • Re: Unique problem
    CHRIS PRIEST -- Friday, 2 April 2004, at 12:15 a.m.
    • Re: Unique problem
      Danny Wright -- Friday, 2 April 2004, at 10:13 a.m.
      • Re: Unique problem
        Sushil Shirodkar -- Saturday, 3 April 2004, at 5:01 p.m.
  • Re: Unique problem
    Sushil Shirodkar -- Friday, 2 April 2004, at 8:41 a.m.
  • Re: Unique problem
    Sushil Shirodkar -- Wednesday, 7 April 2004, at 12:49 p.m.

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