On Fri, May 9, 2008 at 5:34 PM, Peter Teoh <htmldeveloper@xxxxxxxxx> wrote: > > Specifically on this - uniform extent size - it will not prevent or > ELIMINATE fragmentation, right? My understanding is that it will > only reduced the probability of getting fragmented. The simple > reason (*Please correct me!!!*) is because when all the extent sizes > are uniformly the same, it is much easier to allocate/deallocate > stuff, and thus implement the defragmentation algorithm to reorganize > it in contiguous format, correct? > It eliminates tablespace fragmentation. > > > Table/Index fragmentation: > > When the extents of a table or index are scattered all over a tablespace, > it > > is said to be fragmented. > > Unlike memory, where access time almost zero, accessing the disk is > much slower. So sometimes I thought it will be better to spread out > the data - thus enable simultaneous read by the different heads in the > disk, just like those RAID design. Ie, fragmentation via > distribution the blocks out in the disk can improve performance - can > such things happened? > You don't have any control over which track on the disk your data is put. In a carefully crafted test environment you could have this sort of control, but not normally in a production system. If your data is on RAID, then it is separated across several disks already. > For FTS scenario, if the blocks are NOT arranged contiguously, BUT > UNIFORMLY sparsed out somehow, (your fragmentation scenario), the disk > head may be possible to read ALL THE BLOCKS CONCURRENTLY instead of > sequentially as in the contiguous design, thus speeding up FTS. > Possible? (Ie, uniform fragmentation is GOOD) > If you had that level of control, there was only 1 session on the database, you might be able to do something like that. Personally, I think you're overthinking this. Do you have a specific performance problem targeted? Or are you trying to determine if you have one? If the the latter, just ask the users, they will tell you. -- Jared Still Certifiable Oracle DBA and Part Time Perl Evangelist