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From:Lars-Erik Bjørk Date:October 30 2008 8:17am
Subject:Re: Unthawable
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Just a small question on the side ...

Do we abort transactions that have been idle for a certain period of  
time to avoid a malicious user keeping transactions open in order to  
fill up our disks?


On Oct 30, 2008, at 1:55 AM, Kevin Lewis wrote:

> Phillip, every database system I know suffers from this problem that  
> you cannot get rid of old parts of the serial log until the old  
> parts do not contain anything from a committed transaction that is  
> not yet on disk in page form.  Pervasive.SQL uses small 500Kb files  
> that keep adding up and filling up the disk.  After the checkpoint,  
> the old ones can be deleted.
> We have the same problem, except we have only two files at a time.   
> It is always up to the DBA or application designer to try to  
> optimize the database and queries in a way that transactions do not  
> stay open for long enough that the serial log will fill up the disk.
> I think Ann's comment is referring to the likelihood that chilled  
> records will need to be deleted.  Yesterday, I repeated and debugged  
> (a little) the current issue that Chris is seeing with unthawable  
> records. currently tracked by Bug#39696)  We only see it using your  
> Gentest and falcon-record-chill-threshold=4Kb or less.  Sometimes,  
> during this test the same record version will chill and thaw several  
> times.  It is a wonderful stress test.  Even though it is not likely  
> to see in the real world, given enough time, what can happen, WILL  
> Kevin
> Philip Stoev wrote:
>>>> Philip's cases are valuable tests, but not typical usage...  With
>>>> reasonable settings, chills will happen only during loads and mass
>>>> inserts.  The chances of modifying or deleting a record that's been
>>>> chilled are small, and the chances of having a multi-level modify /
>>>> chill / delete cycle are lower still.
>> Please find below an email from Kevin on another thread that  
>> describes a potential chill/thaw/backlogging scenario that is not a  
>> load or a mass insert -- attempting to generate a report by making  
>> multiple passes through the entire data while writing intermediate  
>> values in a summary table. If you decide to mark the start of your  
>> execution by inserting a timestamp in some log table, your  
>> transaction has become an update one and thus the serial log will  
>> grow and the memory will fill up with old record versions.
>> Philip Stoev
>> ----- Original Message ----- From: "Kevin Lewis"  
>> <Kevin.Lewis@stripped>
>> To: "Ingo Strüwing" <Ingo.Struewing@stripped>
>> Cc: "Øystein Grøvlen" <Oystein.Grovlen@stripped>;
> "'dev-backup'" <dev-backup@stripped 
>> >; <falcon-private@stripped>
>> Sent: Wednesday, October 29, 2008 9:28 PM
>> Subject: Re: Restore makes ongoing transactions see empty tables
>>> A single transaction may make a couple passes through a table  
>>> summing up certain columns for certain criteria.  We do not want  
>>> that data to change in the middle of that transaction, for  
>>> example, between pass one and pass two.  Currently, a table will  
>>> be truncated and then the restored data will get replaced within a  
>>> new transaction.  The truncate will be seen immediately by the  
>>> existing transaction, but the restored data, being transactional,  
>>> will not be seen.
> -- 
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UnthawableKevin Lewis25 Oct
  • Re: UnthawableJim Starkey25 Oct
  • Re: UnthawablePhilip Stoev29 Oct
    • Re: UnthawableKevin Lewis30 Oct
      • Re: UnthawableLars-Erik Bjørk30 Oct
    • Re: UnthawableAnn W. Harrison30 Oct
  • Re: UnthawablePhilip Stoev30 Oct
    • Re: UnthawableKevin Lewis30 Oct
      • Re: UnthawableHakan Kuecuekyilmaz30 Oct
      • Re: UnthawableJames Day31 Oct
Re: UnthawableKevin Lewis27 Oct
  • Re: UnthawableAnn W. Harrison27 Oct
  • Re: UnthawableJim Starkey27 Oct