System Recovery Boost

System Recovery Boost expedites a system IPL, restart, and initial user workload after a system outage. With this support, the z/TPF system can deal with a surge in network traffic and recover faster after a system outage.

This support, which is available only for the IBM® z15® or later, provides the following types of boosts:

I-stream boost

I-stream boost enables I-streams that are fenced as part of dynamic CPU capacity to be used during the appropriate boost period.

I-stream boost is turned on in restart when the following conditions are met:
  1. I-stream boost is enabled.
    Note: To enable I-stream boost, use the ZBOST command.
  2. An I-stream cap is set to be less than the number of I-streams defined in the logical partition (LPAR).
  3. The z/TPF system is IPLed on a IBM z15 or later.
When I-stream boost is turned on, I-stream boost remains active for the following period of time:
  • 60 minutes, if the system remains in restart
  • 10 minutes after the system reaches 1052 state, if the system is not cycled to NORM state in that time
  • 20 minutes after the system reaches NORM state

When I-stream boost starts to be turned off, for example, 20 minutes after the system reaches NORM state, the highest I-stream above the I-stream cap collapses. A minute later, the next highest I-stream above the I-stream cap collapses. Every minute another I-stream collapses until the I-stream cap is reached.

Assume that a z/TPF logical partition (LPAR) has 15 active I-streams and the I-stream cap is set to 10. I-stream boost is turned on and causes all of the 15 I-streams to be used. I-stream boost starts to be turned off 20 minutes after the system reaches NORM state:
  1. IS-15 collapses 20 minutes after the system reaches NORM state.
  2. IS-14 collapses 21 minutes after the system reaches NORM state.
  3. IS-13 collapses 22 minutes after the system reaches NORM state.
  4. IS-12 collapses 23 minutes after the system reaches NORM state.
  5. IS-11 collapses 24 minutes after the system reaches NORM state.

After IS-11 collapses, the process of turning off I-stream boost is completed.

Speed boost

Speed boost enables central processors on subcapacity machines to run at full capacity during the appropriate boost period.

Speed boost is turned on in restart when the following conditions are met:
  1. Speed boost is enabled.
    Note: To enable speed boost, use the ZBOST command.
  2. The z/TPF system is IPLed on a IBM z15 or later, and the IBM z15 is a subcapacity machine. A subcapacity machine is an IBM Z® machine where the processors are running below their full capacity.
Note: Speed boost is not turned on if a loader general file or standalone dump tape is IPLed.
When speed boost is turned on, speed boost remains active for the following period of time:
  • 60 minutes, if the system remains in restart
  • 5 minutes after the system reaches 1052 state, if the system is not cycled to NORM state in that time
  • 15 minutes after the system reaches NORM state

When speed boost is turned off, the z/TPF LPAR runs at the subcapacity speed of the machine.

In addition, speed boost is turned on after a ZRIPL command or a catastrophic dump that results in an IPL. In this case, speed boost remains active for up to 15 minutes or until the software IPL that the system performs enters IPL program IPLA, whichever comes first. After the system reaches the initializer program (CCCTIN), speed boost is turned on again, and the standard rules for turning off speed boost are applied.