Sorry for the delay on this answer. Here it is at last.

The sync cost ratio is the average 'log file sync' time divided by the average
'log file parallel write' time. The 'log file parallel write' time is the amount
of time taken for each redo write. The 'log file sync' time is how long
processes had to wait for LGWR to sync a particular redo block. If LGWR is
already writing a particular block when another process begins to wait for it,
then the sync wait will be brief relative to the log file write time. Whereas if
LGWR has not yet started the write and has any sort of performance problem then
the sync wait will be longer than an average log file write time.

The bottom line is that if 'log file sync' waits represent a significant
component of your response time (and they often do) then you should not be
content with a sync cost ratio greater than 1.


-----Original Message-----
Sent: Saturday, 12 August 2000 0:58


I would like to know what do you mean by Sync Cost Ratio?