Do extents impact speed?

I am managing a number of systems that were built before I was involved. Many of these have a large number of extents. There are many tables with more than 150 extents. As an old hand at Turbo, Online, and IDS, my gut reaction was that we would suffer performance problems with large tables like this. But am I right? And how can I prove it? Your ideas, as always, would be much appreciated. regards Malcolm

<mweallans@panacea.co.uk> wrote in message news:1125682132.172443.315300@o13g2000cwo.googlegroups.com... > I am managing a number of systems that were built before I was > involved. Many of these have a large number of extents. There are many > tables with more than 150 extents. As an old hand at Turbo, Online, > and IDS, my gut reaction was that we would suffer performance problems > with large tables like this. But am I right? And how can I prove it? It Depends. If your system is configured to physically allocate the disk space on spindles, then maybe. However, with most modern systems, there is so much software logic between the memory buffer and the physical disk, then a lot of the reasons for trying to keep a single extent are not valid. If you have raid-5, then - well --- who cares.... ;-) A bit of history here. With online we used to make a big deal about having more than 8 extents. That was because in the software at that time, we only cached the first 8 extents of a table in memory, which means that past 8 extents, we had to read the extent list from the partition page. But those days are long gone -- ancient history. Since it has been years since I have looked at V5, I don't know if that is still the case or not, but with v7, v8, v9, and v10, we don't have the 8 extent issue. > > Your ideas, as always, would be much appreciated. > > regards > > Malcolm >