Thanks for the clarification.
get4ked_at_yahoo.com (Ford) wrote in message news:<b2b9197f.0108200937.50594284_at_posting.google.com>...
> It just keeps rolling it back - since re-creating the block image will
> also bring back the older ITL.
>
> stan_mowers_jr_at_yahoo.com (stan mowers) wrote in message news:<b37781b8.0108191514.45ad19e4_at_posting.google.com>...
> > Hi,
> >
> > I was interested in knowing how Oracle creates a Consistent Read
> > version
> > of a block in cases where the ITL entry in the block itself has been
> > over written by subsequent transactions.
> > In case there are live transactions affecting a block, it is
> > relatively easy to create a CR copy by linking the affected rows on
> > the block to the ITL and then linking back to the Undo block from
> > there on. This is only possible as the ITL would always contain valid
> > information for live ( uncommitted) transactions.
> > However, if this ITL entry itself has been overwritten by subsequent
> > transactions affecting the same block but different rows, how does
> > Oracle know which Undo block to read for creating CR copies of the
> > block as they were during the previous transactions. Any information
> > would be appreciated
> >
> > Stan Mowers
> > Sr. Oracle DBA
> > New York
Received on Tue Aug 21 2001 - 08:48:48 CDT
