HPRCLKRT start option

The HPR clock is the mechanism that processes the timer requests for all RTP pipes. The HPRCLKRT start option specifies whether the HPR clock runs in standard or adaptive mode. These modes control how reactive VTAM® is to the packet loss that occurs on RTP pipes that run over Enterprise Extender.

Guideline: Use the default value of HPRCLKRT=STANDARD when you are not running Enterprise Extender.

HPRCLKRT=ADAPTIVE

Specifies that the HPR clock operates in adaptive mode. Running the HPR clock in adaptive mode enables the clock to toggle between standard and high modes of operation when the clock is servicing RTP pipes that are experiencing packet loss. When packet loss occurs, the clock speed adapts to run in high mode. The RTP pipes that are experiencing packet loss are scheduled more frequently, which enables the RTP pipes to recover more quickly. There might be some CPU overhead for running the HPR clock in high mode. When packet loss is no longer occurring, the clock returns to the standard mode.

The adaptive mode is designed to increase the overall performance of RTP pipes when packet loss is occurring. However, RTP performance and CPU overhead are system dependent and might vary.

Restriction: If you code HPRCLKRT=ADAPTIVE, the following restrictions apply:

• This mode is meaningful only in Enterprise Extender configurations that have a defined capacity of 1 Gb or higher access speeds.
• Do not use this mode for uniprocessor configurations or in configurations that are CPU bound.

HPRCLKRT=STANDARD

Specifies the HPR clock is to operate in standard mode. The HPR clock will run at the standard interval to service RTP pipes. Standard mode is the default mode for the HPR clock rate.