Re: Updates synced to disc???
Date: 30 Nov 1994 05:44:22 GMT
Message-ID: <3bh3fm$okn_at_dcsun4.us.oracle.com>
> >In article <Cz9qIK.Iuq_at_ottnews.shl.com> you write:
> >
> >> I have read that Oracle writes are "sync'ed" to disk whenever an insert
> >> or update occurs. This to ensure data integrity.
> >>
> >
> >Surely not? DBWR writes updates to disc when a "checkpoint" occurs.
> >Data integrity is ensured by storing before-image and after-image in
> >rollback segments. Writing to sequential rollback-logs
> >SHOULD be much faster than writing the row changes.
> >
> >... sorry if this is wrong... the views of a non-DBA
> >
> >--
> >John Thomas, Oracle Team Leader E-Mail: John_at_toronto.demon.co.uk
> >The shorter the sig, the smarter the author. Tel: 0181 944 9858
Not quite true.
Oracle guarantee's the integrity of a transaction when LGWR complete's
it's write to the redo log file. DBWR writes are asynchronous to LGWR.
The redo log buffer contains the changed values to the row, and also
the undo information related to the rollback segments; it's this
information that gets written to the redo log file. Should recovery
be required, Oracle uses the information in the redo log file(s)
to "rebuild" the database integrity.
Received on Wed Nov 30 1994 - 06:44:22 CET