Re: Very high 'log file sync' wait time with no 'log file parallel write' wait time

On Fri, 24 Nov 2006 05:52:25 -0800, mccmx wrote:

>
> What is causing this huge amount of 'log file sync' activity..? The
> 10046 trace file seems to suggest that we are committing for every row
> in the table but the count(*) is increasing in line with the 'buffer'
> parameter from the import command.
>
> Is this a bug..?

Matt, how big is your log buffer? Log writer will write

1) Every 3 seconds
2) When there is more then 1M in log buffer
3) When your log buffer is more then 1/3 full
4) When "commit" is issued.

The 10046 trace suggests that you are waiting for log file sync, which means that you're writing to the log file frequently. If your log buffer is too small, it is possible that you're writing after every row. Also, there is a possibility that import will write more then 1M of redo entries, if your dump file contains a LOB field. In that case, buffer/commit combination in the import parameters will not help you much. Have you checked V$SESSION_EVENT and V$SESS_TIME_MODEL? V$SESS_TIME_MODEL is something that gives you the
Also, this is probably a stupid question, but how frequently are you performing checkpoints and log switches?

-- 
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