IDS Forum

RE: Lock Table Overflow

Posted By: Robert Roussey(IT)
Date: Thursday, 6 March 2008, at 6:26 a.m.

In Response To: Re: Lock Table Overflow (Art S. Kagel (Oninit))

RedHat AS3 U8, IDS 10.00.UC4 (32-bit)

With a bad query that I haven't nailed down yet (might be free-form
SQL) locks max out at 2,000,000.
Unfortunately, this causes the locking mechanism to become not friendly.
At some point locks become phantom (?) and all other users get lock
errors. A bounce of the db engine is required.

Bob Roussey
Unix / Informix Administration
Spirit Airlines
Robert.Roussey@SpiritAir.com

-----Original Message-----
From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of
Art S. Kagel (Oninit)
Sent: Thursday, March 06, 2008 1:30 AM
To: ids@iiug.org
Subject: Re: Lock Table Overflow [11507]

Long Nguyen wrote:
> Thanks Art,
> I intend to increase the max number of locks (because the SP was
written by
> a consultant long time ago and it is so complicated that I dare not
touch
> it!!).
> in onconfig (from 500000 to 2000000). Does this have any implications
on
> system performance? and the change will be dynamically implemented or
need
> to bounce the engine?
>

Each lock is from 44 to 120 bytes depending on the platform and whether
you are using a 32bit or 64bit engine version (you are on 64bit so
figure 120 bytes per lock to be safe). The only issue is whether the
additional memory will cause swapping on the system whether for IDS or
for other apps. You know how much free memory is on the system.

You have to bounce the IDS instance for LOCKS changes to take effect.

Art S. Kagel
Oninit

> Regards,
> Long N
> ===============
>
> "Art S. Kagel
>
> (Oninit)" To: ids@iiug.org
>
> <art@oninit.com> cc:
>
> Sent by: Subject: Re: Lock Table Overflow [11504]
>
> ids-bounces@iiug.
>
> org
>
> 06/03/2008 11:07
>
> AM
>
> Please respond to
>
> ids
>
> Long Nguyen wrote:
>
>> Hi all,
>>
>>
>
> First, it would be much better if your task either acquired a table
lock
> before deleting a million rows or alternatively committed the work
every
> 10,000 -> 50,000 rows instead. You can get my dbdelete.ec utility for
> this. It is VERY fast and performs partial deletes in transactions of
> 8192 rows at a time be default so it avoids the lock table overflow
> problem. Dbdelete in part of the package utils2_ak which you can
> download from the Oninit web site (www.oninit.com) or from the IIUG
> Software Repository. Note that new releases of my utilities will now
> appear on the Oninit site a few weeks prior to posting to the IIUG
> Repository.
>
> Second, IDS 9.40 and later do indeed expand the lock table if it's
> capacity is exceeded. The documentation is ambiguous about how this is

> done. In different places the descriptions are different and
> contradictory. In one location the docs say that the table will be
> expanded up to the maximum number of locks or 8,000,000. In another it

> says that each time the table is exhausted its size is doubled up to
15
> times (starting with 500,000 locks that would take you to 1million
> immediately and to 20,000,000,000 locks eventually) which can easily
> become greater than the max. Another location states that while the
> table size is doubled, no more than 100,000 locks are added at a time.

> For you this would mean adding 1,500,000 locks to bring you up to
> 2,000,000. On the other hand you didn't experience any of these
> scenarios. Curious.
>
> Maybe John Miller III can comment? And get the docs fixed (I was
> looking at the 11.10xC2 docs)!
>
> Art S. Kagel
> Oninit
>
>
>> This may be an old question but...
>> We had a replication job that triggered the deletion of more than 1
>>
> million
>
>> records on a small table while the maximum number of locks in the
>>
> onconfig
>
>> file is 500000.
>> We got
>> 11:26:43 Lock table overflow - user id 104, session id 360387.
>> 11:26:44 Process exited with return code 1: /bin/sh /bin/sh -c
>> /usr/informix-10
>> ..00.FC4/alarm.sh 3 21 "Dynamic Server resource overflow: 'Locks'."
"Lock
>>
>
>
>> table overflow.
>> 11:26:46 CDR CDRD_4215: transaction aborted (All rows in a
transaction
>> defined
>> with row scope were rejected) with sql error 0 isam error 0.
>>
>> The system did automatically rollback afterward but all other
>>
> transactions
>
>> were blocked during that long time because no available locks.
>> Searching online answers we found some help like this:
>> "Depending on the version of the engine IDS will automatically add
more
>> memory for the locklist till 8 million locks.
>> Or you just need to increase the value of Locks in the onconfig
file."
>>
>> Our engine (IDS 10.00 FC4WC) seemed not increase the numebr of locks
to 8
>>
>
>
>> millions.
>> So the only resolution is to increase the LOCKS in ONCONFIG from
500000
>>
> to
>
>> say 2000000.
>> Is that the only way to prevent the overflow of the lock table ?
>> Any help would be appreciated.
>> Regards,
>> Long Huy Nguyen
>> MIS(Analyst Programmer)
>> Ruralco Limited
>> P.O.Box 515
>> Wentworthville NSW 2145 Australia
>> (Ph) 02 9688 8528 (Fax) 02 9896 7763
>>
>>
>
>
>
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See you at the IIUG Informix 2008 Conference
The Power Conference for Informix Professionals
April 27 - 30, 2008 Marriott Overland Park (Kansas City), Kansas
http://www.iiug.org/conf
Registration Now Open!!

Messages In This Thread

• Lock Table Overflow
  Long Nguyen -- Wednesday, 5 March 2008, at 7:30 p.m.
  • Re: Lock Table Overflow
    Art S. Kagel (Oninit) -- Wednesday, 5 March 2008, at 8:07 p.m.
    • Re: Lock Table Overflow
      Long Nguyen -- Wednesday, 5 March 2008, at 8:36 p.m.
      • Re: Lock Table Overflow
        Art S. Kagel (Oninit) -- Thursday, 6 March 2008, at 1:30 a.m.
        • RE: Lock Table Overflow
          Robert Roussey(IT) -- Thursday, 6 March 2008, at 6:26 a.m.
          • Re: Lock Table Overflow
            tilleul17@web.de -- Monday, 10 March 2008, at 5:19 a.m.
            • Re: Lock Table Overflow
              Walter Lowich -- Monday, 10 March 2008, at 6:16 a.m.

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