Re: Can a large log buffer cause data loss?

The log buffer is triggered to write

1. When it is 1/3 full (at least that's the default) or
2. When a commit is issued

so the risk of losing committed data is very small. Also, when a user issues a COMMIT it is not acknowledged until the log file has been written.

However, there is a small window of opportunity for a user to issue a commit and have the system crash before log writer has finished the write. Arguably the user may say that their data has 'been lost'; since they will not have received a 'commit complete' message though, their data has not been 'lost', it has simply not been committed and on database recovery the work done in their attempted transaction would be rolled back.

--

Jonathan Lewis
Yet another Oracle-related web site: http://www.jlcomp.demon.co.uk

Magnus Bergh wrote in message ...
>hI am not so sure about how the log_buffer parameter works. Does the
>buffer work as a cache (wait to write until log buffer is full or some
>other criteria) or is it used to avoid wait when the LGWR process is busy
>writing to log files.
>
>if log buffers is used as a cache, couldn't this cause data loss if the
>Oracle instance crash? Then all buffers in the cache would be lost. I
>hope and don't think it is this way, but I want to be sure.
>
>Magnus
Received on Tue Sep 21 1999 - 03:03:48 CDT