Re: RAC vs OPS

"Pete Sharman" <peter.sharman_at_oracle.com> wrote in message news:<HRd68.6$8X1.93_at_inet-nntp1.oracle.com>...
> I may not be understanding your issue correctly here, but the log buffer
> flush is not tied to the block transfer through the interconnect AFAIK. The
> log buffer flush is an independent event.
>

Well,
this is citation from Oracle9i Real Application Clusters Deployment and Performance Guide, chapter 6:
"
Elimination of I/O for Forced Disk Writes of Blocks Cache Fusion practically eliminates disk I/O for data and undo segment blocks by transmitting current block mode versions and consistent-read blocks directly from one instance's buffer cache to another. This can reduce the latency required to resolve writer/writer and reader/writer conflicts by as much as 90 percent.
Cache Fusion resolves concurrency, as mentioned, without disk I/O. Cache Fusion expends only one tenth of the processing effort that was required by disk-based parallel cache management. To do this, Cache Fusion only incurs overhead for:

Pinning a current block, logging the changes to the block, forcing a

log flush, and sending the block    
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Or when requesting a consistent read version:

Processing the request and constructing a consistent-read copy of the requested block in memory and transferring it to the requesting instance

On some platforms this can take less than one millisecond. "

Could you clarify this one ?

Regards,
Slava. Received on Fri Feb 01 2002 - 01:16:18 CST