Re: Redo Log Mechanics Question

To make full recovery possible, we need run the instance with ARCHIVE LOG mode then we can go for recovery.

With NO ARCHIVE LOG mode, we cannot recover the database after the latest full backup.

vimal

Roger Westbrook <rwestbrook_at_dollargeneral.com> wrote in article <375FF8D8.61488FD3_at_dollargeneral.com>...
> My understanding of how the redo log system works must be missing
> something because I don't understand what good it could do for recovery.
>
> Here's what I think I know; Uncommitted transactions are stored in the
> Redo Log Buffer until a commit, a checkpoint, a LGWR timeout, or 2/3rds
> full. LGWR then flushes everything to the online Redo Log Files. When
> a Redo Log Group is full there is a log switch. This kicks off a
> checkpoint. A checkpoint causes all dirty db buffers covered by the log
> to be flushed to datafiles.
>
> Here's what I don't understand... what happens to an UNcommited
> transaction? If a transaction is uncommitted at the time of a Log
> Buffer flush then it sounds like it gets written to the Redo Log Files.
> If it's still uncommitted at the time of a log switch then what
> happens? Will it eventually be overwritten as the Redo Log Files come
> full circle and that particular group gets overwritten? Am I correct in
> assuming that this would make instance recovery impossible?
>
> Thanks in advance!
> Roger Westbrook
> sidhe_at_home.net
>
>
Received on Thu Jun 10 1999 - 20:08:42 CEST