Is disk I/O tuning obsolete?
Today’s disks devices are much more sophisticated than the 3350/3380/3390 devices. New devices employ internal cache and buffers, internally perform asynchronous I/O, etc. Therefore, many old disk I/O tuning considerations (e.g., disk head movement consideration; placement of data sets relative to the VTOC) are now obsolete. However, optimizing I/O still provides significant enhancements with regard to overall CPU and execution time. Optimization eliminates unnecessary activities and delays both before and after “the I/O request is handled by the sophisticated hardware device.” When an application issues a read/write request, some operating system routines (e.g., access method routine and input/output supervisor) receive control. These routines perform a large number of tasks such as I/O operation preparation, start I/O initiation, buffer pool management, and I/O interrupt handling. The operation of the MVS routines entails significant CPU costs. By reducing the number of I/O operation
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