Turning on System Recovery Boost

System Recovery Boost is enabled by default, and is controlled by the BOOST= parameter in your IEASYSxx member of parmlib. The default, BOOST=SYSTEM, means that z/OS takes advantage of whatever boosts are available to it, given the system configuration. BOOST=ZIIP allows only zIIP boosting, while BOOST=SPEED allows only speed boost. BOOST=NONE disables all types of boosting.

The system command DISPLAY IPLINFO,BOOST shows the value of the BOOST system parameter. The system command DISPLAY IPLINFO,BOOST,STATE displays information about System Recovery Boost use, whether or not boosts are currently active, whether or not recovery process boosts are enabled for use, recovery boost time since IPL, and, with the z16, additional details about recovery process boost time use: available, used, remaining and time until refresh. For details, see message IEE258I in Messages.

There are also indicators on the HMC that can show if an image is currently boosting or not. With the z16, the HMC also shows current usage of recovery process boost time. The Image Detail panel indicates if an image is boosting, and columns in the Systems Management list and Custom Groups list indicate if a boost is active and which types are active.

Startup and shutdown boost

For each image, System Recovery Boost can be used once during IPL and once while shutting down the system, as follows:

IPL boost is activated automatically during IPL and lasts for one hour.
You start shutdown boost by using the START IEASDBS command.

For more information, see IPL boost, and Shutdown boost.

Recovery process boost

Recovery process boosts can be used many times during an IPL. They are based on recovery events, including HyperSwap processing, coupling facility structure recovery, sysplex partitioning recovery, and, with the z16, SVC dumps, middleware region startup as well as loading HyperSwap configuration information. You can dynamically enable or disable all recovery process boosts with the IEASRB proc. For more information, see Recovery process boost.

BOOST parameter in IEASYSxx

Two boosts are possible: zIIP boost and speed boost. These boosts are available when running z/OS® on a machine with IBM z15™capabilities only.

The zIIP boost configures online zIIPs in the standby state in accordance with the zIIP configuration of the LPARs. The zIIP boost will "blur" work between standard CPs and zIIPs. (That is, work that is normally eligible only for a standard CP may be run on a zIIP.) zIIP boost only applies to an LPAR that, at the time of boost activation, meets all of the following criteria:

Has at least one online or standby zIIP
Is not a dedicated partition
Is running with HIPERDISPATCH=YES

In order for zIIPs to be configured online during boost processing, the zIIPs must be defined to the LPAR. They may be defined before IPL or they may be dynamically added to the configuration after IPL, depending on the LOADxx DYNCPADD parameter value in effect. zIIPs dynamically added after IPL do not apply to IPL boost but could be used by shutdown boost.

The speed boost makes a sub-capacity standard CP run at the speed of a (full-speed) zIIP. Speed boost only applies to an LPAR that, at the time of boost activation, does not have its standard CP(s) already running at the (full-capacity) speed of a zIIP.

SYSTEM: Apply system rules. If the machine does not support boosts, treat as NONE. If the system does support boosts, activate all boosts that the machine supports.
ZIIP: Activate only the zIIP boost. Do not activate the other (speed) boost.
SPEED: Activate only the speed boost. Do not activate the other (zIIP) boost.
NONE | NO: Do not activate either of the boosts.