Data prefetch optimization for AIX systems on POWER architecture

You can use Data Stream Control Register (DSCR) to control the enablement, depth, and data prefetch settings for an AIX® system on the POWER® architecture.

When you activate data prefetch on an AIX system, the applications that contain predictable data access patterns might benefit from data prefetching. For such applications, you can set the operating system prefetch depth or use the setting that is most beneficial. If aggressive data prefetching is set, the performance might degrade for applications that contain unpredictable data access patterns.

You can view the current settings of the hardware stream mechanism and set a system-wide value for DSCR. You can set or unset the prefetch depth for an AIX system on the POWER architecture temporarily or permanently. Use the root user privileges to set or unset DSCR.

When you set or unset DSCR, consider the following points:

• Set DSCR only if the server maximizes the amount of information that it is able to access with minimum memory latency.
• Unset DSCR on a partition, only if the setting benefits all the applications that are running on the partition. You must consider the effect on application throughput and processor usage when you evaluate the performance.