If I recall, there is "end of extents" checking that happens whenever you cross an extent boundary; plus in the "old days" extents would cause seek time as you moved to the location of the new extent. If the PDS was on a very active pack and poorly allocated, you could have the first extent at the beginning of the pack, the second near the end, then the third back near the beginning, etcetera, resulting in what was called "thrashing the heads". In the days before our volumes were cached and virtualized we seemed to spend some time and money on dataset placement.
Tim Hare Senior Systems Programmer Florida Department of Transportation (850) 414-4209 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
