When I hear that one about "this is datawarehouse", I'm always reminded of the argument "datawarehouses are large and do a lot of reads". I wonder how they became large in the first place? Perhaps through "lots of reads"? And if they don't get updated often, I doubt the "lot of reads" would be of any interest... Coming back to block sizes: in the mainframe environment, I'd definitely consider a larger block size for a large db, datawarehouse or not. This mostly because one can configure the I/O of mainframes to bypass most of the intervening handlers and indeed realize the benefits of a larger block size form the POV of a db. With other environments, this is much more difficult: the I/O path of any given process in Linux, Unix and so on, is not well defined or known and may change at a patch's notice. Hardly the best way to handle arcane I/O configuration decisions. Outside of mainframes, I'd leave the block size at 8k except for special cases: for a small-ish db, I'd check first if it has to store lots of volatile LOBs. If so, then increase the block size. Volatile LOBs don't go well with small block sizes, particularly with Oracle. I doubt the common advantages a larger block size can bring (reduced header overhead, reduced metadata maintenance) can be realized at smaller scales. I also nowadays have serious doubts of Oracle's storage layer stability when using anything other than 8K blocks. The number of bugs in the online place related to handling non-8k block sizes is staggering. All practical considerations, really. Nothing to do with theoretical potential advantages of larger block sizes for certain workloads. These can be relevant IF all other factors are controlled and pegged down. Hardly the case when your OS is from one stable, your I/O SAN is from another, your db is yet from another. Cheers Nuno On Tue Oct 27 2:32 , Niall Litchfield sent: >so, discussion with DW architect today > >"but this isn't OLTP,this is DW, in a datawarehouse you want the biggest block size you can have". > >my question to you (and him) > >"why? What's the theory and evidence for this?" > -- //www.freelists.org/webpage/oracle-l