AS/400e Advanced Technology
54 AS/400e System Handbook
storage subsystem level, caches data for the set of disks that are within that specific
subsystem. Therefore, it is logical to add Extended Adaptive Cache to the most active and
performance-critical storage subsystems within the system. For example, Extended Adaptive
Cache is not designed to work with compressed user ASPs. This is because accessible
cost-effective storage is the typical goal for compressed disks, as opposed to lightening-fast
performance.
The larger the area of disk storage that is actively receiving I/O requests, the more selective
Extended Adaptive Cache is about when to bring new data into cache. This adaptive ability
allows Extended Adaptive Cache to be effective on many workload types and sizes. The
overall cache effectiveness is best understood from this perspective by using Extended
Adaptive Cache Simulator.
Extended Adaptive Cache Simulator
Extended Adaptive Cache Simulator is a performance tool that provides estimates of DASD
I/O response time improvements and prediction of the number of disk reads that could be
saved through the use of Extended Adaptive Cache operations. This determination is based
on your system configuration and application environment and is made before you purchase
a #4331/#6831 Read Cache Device.
Extended Adaptive Cache Simulator is controlled within the AS/400 Management Central
collection services and is already available on V4R4 systems with #2748 PCI RAID Disk Unit
Controller. Within the Simulator, flexibility exists to emulate different cache capacities to
better determine the capacity that would best suit your specific system and workload needs.
Extended Adaptive Cache Simulator Restrictions and Considerations
• A storage controller (#2748/#4748) capable of supporting Extended Adaptive Cache is
required for Extended Adaptive Cache Simulator.
• Extended Adaptive Cache Simulator is enabled and disabled by the user through
AS/400 Operations Navigator, Management Central, or Collection Services.
Performance Tools LPP (5769-PT1) is required for Extended Adaptive Cache
Simulator.
• Activation of Extended Adaptive Cache Simulator will not actually improve your
system's performance. It gathers statistical information to predict the performance
improvement that Extended Adaptive Cache could offer.
• Extended Adaptive Cache Simulator and Extended Adaptive Cache cannot be active
at the same time on the same I/O adapter.
Visit the AS/400e Information Center Web site at:
http://publib.boulder.ibm.com/html/as400/infocenter.html
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