Re: how synchronous is Oracle?

There are a couple of very special cases, but there are a couple of very special
cases.

Someone has already mentioned the
what will happen if you

    set transaction read only;
in session B before session A does
it's thing. There is also the 'serializable' isolation level which will have a similar effecit. These are two examples of the
same type of thing, though, and require
session B to be coded to use non-default behaviour.

The other catch comes from RAC (or OPS). If session B is on a different instance from session A then there is a window of up to 3 seconds (by default) where session B may not see a committed change from session A even though session B starts its query after session A issues its commit.

--
Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html


"Robert A.M. van Lopik" <lopik_at_mail.telepac.pt> wrote in message
news:3e66fee5$0$10173$a729d347_at_news.telepac.pt...


> Consider the following scenario:

> I have two processes, A and B. process A logs on to the database,

inserts a


> record into a table, logs of and signals (one way or another)

process B.


> Process B was already logged on and does a select that should

retrieve the


> record just inserted.

> The question is: does Oracle guarantee that committed inserts are

> "immediately" visible to other users, or is there a possibility,

e.g. on a


> heavily loaded system, that proces B will not retrieve the record,

although


> it will see it at a somewhat later time?

>

> I found a thread in this forum about serializability around 1999,

but that


> was too theoretical for my liking. For now I just would like to rule

out the


> possibility that records would not be immediately visible, or learn

how to


> make this happen if the guarantee is not there.

>

> B.T.W. The concrete question is about Oracle Version 8.1.7

>

> Thanks,

> Rob van Lopik

>

>