Hi Alan, yes, this was new to me too. In another mail Grzegorz Goryszewski have just posted a link to an article by Alex Gorbachev, which seem to confirm that too: Quoting it: Traditionally, it’s common to assume that the closer to 100% utilization a device is, the more saturated it is. This might be true when the system device corresponds to a single physical disk. However, with devices representing a LUN of a modern storage box, the story might be completely different. [...] Regards Dimitre -- //www.freelists.org/webpage/oracle-l