Re: Transaction Gradually Slows to a crawl! (please help)

"Daniel Morgan" <damorgan_at_exxesolutions.com> wrote in message news:3ED4C338.B060678D_at_exxesolutions.com...
> Richard Foote wrote:
>
> > "Ryan" <rgaffuri_at_cox.net> wrote in message
> > news:g_UAa.115250$823.9886_at_news1.east.cox.net...
> > > how do you disable redo logs? you can generate no redo? really? i have
a
> > > staging database also.
> > >
> >
> > Hi Ryan,
> >
> > By setting "_disable_logging"=true
> >
> > Note though that this is a somewhat naughty, unsupported and risky thing
to
> > do .....
> >
> > Note also that if your database is in archivelog mode, it's does rather
> > nasty stuff to the statuses of the poor online redo logs and they'll
> > probably need to be re-created when you set it back to false again.
> > Therefore if you were to ever set the above, I would recommend placing
the
> > database in noarchivelog mode first.
> >
> > Note also (last one I promise) that poor LGWR has an incredibly
frustrating
> > time of it in that it is still being pinged to perform it's writes but
> > nothing happens. It's rather good fun watching your log write times
start to
> > go up and up and up ...
> >
> > Not that I've ever done it of course ...;)
> >
> > Cheers
> >
> > Richard
>
> Ok Richard I'll play along. Hypothetically, of course as you've never done
it,
> what happens with this parameter setting when you update a single row and
type
> commit? Does it hold everything in a buffer and then write directly to the
> datafile or does it kill performance by writing it out immediately?
>
> --

Hi Daniel

The rest of the database remains unchanged. The buffer cache works in exactly the same way, old buffers get overwritten, old dirty buffers get written to disk. It's just the process of physically flushing the redo buffer that gets disabled.

Actually, I have used it (you got it out of me :)

I used it in a very large test environment where I wanted to perform a massive amount of changes (a process to convert blobs to clobs actually) and it was going to take days to complete. By disabling logging, I completed the task in hours and if anything untoward were to have happened, I was quite happy to restore the test database back from backup.

Like I said, it's not something I'm comfortable recommending to folks at there but everything in life has it's use ...

It's a question of knowing the risks, the repercussions and the possible benefits.

Cheers

Richard Received on Wed May 28 2003 - 09:33:30 CDT