pending Sequential prefetching in Adaptive Replacement Cache (SARC) places data in cache based not only on server access patterns, but also on frequency of data utilization.
1.4.3 IBM multipathing software
IBM
Most vendors’ priced multipathing software selects the preferred path at the time of initial request. IBM's free of charge preferred path multipathing software offers performance beyond
this, by dynamically selecting the most efficient and optimum path to use at each data interchange during read and write operations.
1.4.4 Performance for zSeries
In this section we discuss some z/OS relevant performance features available on the DS6000 series.
Parallel Access Volumes (PAV)
PAV is an optional feature for zSeries environments which enables a single zSeries server to simultaneously process multiple I/O operations to the same logical volume, which can help to significantly improve throughput. This is achieved by defining multiple addresses per volume. With Dynamic PAV, the assignment of addresses to volumes can be automatically managed to help the workload meet its performance objectives and reduce overall queuing. To utilize dynamic PAV, the Workload Manager must be used in Goal Mode.
Multiple Allegiance
Multiple Allegiance is a standard DS6800 feature which expands simultaneous logical volume access capability across multiple zSeries servers. This function, along with the software function PAV, enables the DS6800 to process more I/Os in parallel, helping to dramatically improve performance and enabling greater use of large volumes.
Priority I/O Queuing
Priority I/O Queuing improves performance in z/OS environments with several z/OS images. You can, for example, favor I/O from production systems compared to I/O from test systems. Storage administrator productivity can also be improved and Service Level Agreements better managed due to this capability.
Chapter 1. Introducing the IBM TotalStorage DS6000 series 19
