Re: Monitoring occurence of snaphot too old

Well, 1555 happens when the query is unable to construct a read consistent version
because rollback segment blocks have been reused by other transactions. The only solution
is to
a) have sufficiently large rollback segments so that a transaction can

    get unused rollback segment space without reusing recently allocated space.
b) NOT have very long running queries.

Conceptually, in my opinion, the infamous "snapshot too old" comes from mixing
DW and OLTP functions in the same database. A good practice is to have a "reporting
database" as a separate instance and populate it in some way (replication, SRDF,
standby, self written programs). The reporting database can then be re-indexed with
bitmap indexes and used for reports only. Things like that are (now this is for DW
purists) called ODS or opeational data stores and are populated approximately once a
week. Only very small daily reports are run against the main OLTP database.
If you separate your functions like that, ora-1555 will become a distant memory.

On 2002.08.02 19:23 Mohammed.Ahsanuddin_at_VerizonWireless.com wrote:
> Hi,
>
> Yes, it is 8i..I was more interested in catching snapshot too old
> before it
> happens..does not seem possible..
>
> But, my thanks to everyone who responded..
>
> Mohammed Ahsanuddin
> Oracle DBA
>
>
>
> -----Original Message-----
> Sent: Friday, August 02, 2002 2:19 PM
> To: Multiple recipients of list ORACLE-L
>
>
> Yes. I didn't see the version it the other guy's post.
> Was it 8i?
>
> > -----Original Message-----
> > From: Farnsworth, Dave [mailto:DFarnsworth_at_Ashleyfurniture.com]
> > Sent: Friday, August 02, 2002 1:54 PM
> > To: Multiple recipients of list ORACLE-L
> > Subject: RE: Monitoring occurence of snaphot too old
> >
> >
> > Isn't the UNDO_RETENTION parameter a new one for 9i and does
> > not exist in 8.x and lower.
> >
> > Thanks,
> >
> > Dave
> >
> > -----Original Message-----
> > Sent: Friday, August 02, 2002 12:05 PM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > Just set the UNDO_RETENTION parameter to 4 hours and forget
> > about the 'snapshot too old'. It's no longer happening.
> >
> > > -----Original Message-----
> > > From: Mohammed.Ahsanuddin_at_VerizonWireless.com
> > > [mailto:Mohammed.Ahsanuddin_at_VerizonWireless.com]
> > > Sent: Friday, August 02, 2002 12:14 PM
> > > To: Multiple recipients of list ORACLE-L
> > > Subject: Monitoring occurence of snaphot too old
> > >
> > >
> > > Dear List members,
> > >
> > > I was wondering if there is a way to monitor the database and
> > > tell if there
> > > is a possiblility of snapshot too old error occurence.
> > >
> > > Any input is highly appreciated..
> > >
> > > Thanks
> > >
> > > Mohammed Ahsanuddin
> > > Oracle DBA
> > >
> > > --
> > > Please see the official ORACLE-L FAQ: http://www.orafaq.com
> > > --
> > > Author:
> > > INET: Mohammed.Ahsanuddin_at_VerizonWireless.com
> > >
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> 538-5051
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-- 
Mladen Gogala
-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Mladen Gogala
  INET: mgogala_at_adelphia.net

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
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