Re: Oracle read consistency *inside*a transaction

Please see below:

[AF]
<afilonov_at_yahoo.com> wrote in message
news:1102377411.931512.29600_at_f14g2000cwb.googlegroups.com...
> True, but irrelevant for the transaction itself. It doesn't do
> consistent
> read in this case. It would if other transactions modified the block,
> but
> you said it's not the case. For the session in which transaction
> happened, all changes done by this transaction are visible, i.e. there
> is no need for rollback.

[VC]
Oracle performs intra-transactional 'mini'-rollbacks aka 'consistent reads' in several cases:

1. A failed update/delete/insert statement.
2. savepoint ... rollback to.
3. apparently in the case I described in my original message.

It's sort of obvious that no other transaction is involved during those 'consistent reads' in order for them to qualify as such.

[VC]
>
>> The rest of your response is skipped as irrelevant.
>>
>

[AF]
> Well, why are you asking then?
>

[VC]
 I asked hoping to get some insight into how Oracle distinguishes between two different changes in the same transaction. My assumption was that Oracle performed a mini-rollback in order to get the previous row value. What I do not understand is how exactly it's implemented since an SCN can not be used as a 'timestamp' inside the same transaction.

Unfortunately, your remarks were, as said, largely irrelevant. In case I missed something of value in your response, I apologize.

Thanks. Received on Mon Dec 06 2004 - 18:32:36 CST