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
> 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"
>> 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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