FreeTDS Development Group

[Michael Peppler <mpeppler AT peppler.org>]

On Fri, 2002-10-25 at 08:38, Lowden, James K wrote:
> > From: ZIGLIO Frediano [mailto:Frediano.Ziglio AT vodafoneomnitel.it]
> > Sent: October 25, 2002 4:16 AM
> > 
> > I tried with command
> > 
> > 1> dump tran tempdb to 'output.txt'
> > 
> > But it reply with strange error...
> 
> Frediano, 
> 
> I think "dump tran with no_log" is your friend.  That's the old syntax and
> should still work.  

Dump tran with no_log should only be used as a last resort.

In tempdb the log is always automatically truncated on checkpoint - but
as I said if there is a long/large transaction that uses tempdb then you
can certainly run out of log space.

> 
> Sybase's design uses a write-ahead log.  Your query is written to the
> transaction log first, then applied to the data, then marked as "done" in
> the log.  Only then is the transaction considered "committed".  Not until
> then can it be removed from the log.  
> 
> Microsoft moved the log out of the database and put it in the filesystem,
> but its role and purpose were unchanged.  

You can place Sybase transaction logs on its own device as well (in fact
this is recommended). However, again, for tempdb the situation is a
little different.

> The log continues to grow until it is "truncated", meaning that committed
> records are removed.  If the truncation operation saves the records to a
> file, they can be used later as part of an incremental restore operation.
> We have many such "warm standby" machines here: they have a copy of the
> production database, and periodically (say, every 10 minutes) the production
> log is truncated and applied to the standby.  Data loss is thus constrained
> to the truncation window.  For more information, rtfm; look for "Checkpoints
> and the Active Portion of the Log".  

In tempdb (which is what Freddy is using, I believe) the log is
automatically truncated on checkpoint. 

If tempdb doesn't clear up after a restart of the server this means that
there is a transaction in one of the other databases that uses tempdb
space and has been re-applied on startup.

Michael
-- 
Michael Peppler / mpeppler AT peppler.org / http://www.mbay.net/~mpeppler
mpeppler AT zetatools.com / ZetaTools, Inc / http://www.zetatools.com
ZetaTools: Call perl functions as Sybase stored procedures!

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