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 Mon Aug 20 2001 - 12:37:50 CDT
