System Recovery Boost is a new feature of the IBM z15 Models T01 and T02 (M/T 8561 and M/T 8562). Speed Boost is a capability of System Recovery Boost that improves the recovery time of exploiting operating systems when running on a subcapacity machine (CPC). It is designed to provide higher temporary processing capacity to LPARs for speeding up IPL, shutdown, and stand-alone dump operations, without increasing IBM software costs1. It delivers improved overall system and application availability by minimizing the downtime that results from system shutdown and restart operations. See the IBM Redpaper Introducing IBM Z System Recovery Boost (REDP-5563) for further details.
With the PTFs UD54376, UD54377, and UD54378 for APAR DY47832 "SYSTEM RECOVERY BOOST SUPPORT", z/VSE 6.2 provides native support for the System Recovery Boost feature of the IBM z15 Models T01 and T02. This support enables z/VSE to temporarily boost general-purpose processors (CPs) running at subcapacity to full capacity in a LPAR, without increasing IBM software costs1. The Speed Boost lasts up to 60 minutes during system IPL as well as stand-alone dump processing and up to 30 minutes during system shutdown. After the Speed Boost ends, the CPs being used by the LPAR will return to the subcapacity model speed. This increase applies only to the LPAR being boosted; all other LPARs not being boosted will run at subcapacity model speed, and the machine itself will still remain a subcapacity machine.
System Recovery Boost is designed to cause no impact to your IBM software licensing charges. During the boost period, the z/VSE Capacity Measurement Tool (CMT) will record the unboosted capacity of the LPAR image in the SCRT89 records. For clients who are using subcapacity licensing, the SCRT89 records will not record an increase in the available capacity during Speed Boost periods, and thus will not increase your 4-hour rolling average (4HRA)
2. For clients paying for MSU consumption pricing, consumption on general-purpose processors (CPs) accrues as normal, but there is no net increase in consumption, as any work being done during boost would have been done before, just more slowly. For clients paying for full capacity, the total recorded capacity of the CEC doesn’t change, and thus the bill will remain the same.
See the SCRT User’s Guide as well as Using SCRT (Java Version) with z/VSE - Best Practices for details how to setup CMT on z/VSE and how to generate a sub-capacity report using the Sub-Capacity Reporting Tool (SCRT). See Sub-Capacity for z/VSE for additional information unique to z/VSE customers.
The z/VSE Query Virtual Server (QVS) API does also return the unboosted CEC, LPAR image, and z/VM guest capacities. The fields QVSCECCAPACITY, QVSIMGCAPACITY, and QVSVMCAPACITY will not reflect any active Speed Boost. For further information on the QVS API see the description of the macros IWMQVS and IRAQVS in the z/VSE Supervisor Calls and Internal Macros manual.
The manuals z/VSE Administration, z/VSE System Control Statements (sections "SYSDEF SYSTEM" and "QUERY SYSTEM"), and z/VSE Messages and Codes Volume 1 are planned to be updated in the near future.
When the z/VSE system is running under z/VM 7.1 it may transparently benefit from an active IPL or shutdown Speed Boost of the z/VM system. On z/VM 7.1 the PTF for APAR VM66283 “Z/VM SYSTEM RECOVERY BOOST FOR IBM Z15, D/T8561” is required for z/VM to support System Recovery Boost. See the z/VM Migration Guide, section System Recovery Boost for further details.
Requesting an IPL boost
On a subcapacity IBM z15 Model T01 or T02 in LPAR with the PTF UD54376 applied the z/VSE system automatically requests a temporary IPL boost early during IPL and during Stand-Alone Dump processing. An IPL boost lasts up to 60 minutes. The system prints the following message on the console during IPL, which is also recorded in the Hard Copy File (HCF):
BG 0000 0J87I RECOVERY BOOST IS ACTIVE
If the processor (CEC) is running at full capacity the system prints the following message during IPL:
BG 0000 0J87I RECOVERY BOOST NOT ACTIVATED BECAUSE PROCESSOR IS FULL CAPACITY
If the processor (CEC) does not support System Recovery Boost the system prints the following message during IPL:
BG 0000 0J87I RECOVERY BOOST NOT SUPPORTED BECAUSE FACILITY NOT AVAILABLE
When the z/VSE system is running in a z/VM guest no message regarding System Recovery Boost is printed during IPL. z/VSE Stand-Alone Dump (SADUMP) does not print a message either.
Following is a sample IPL console log excerpt of a z/VSE 6.2 system that successfully activated an IPL boost:
BG 0000 0I04I IPLDEV=X'9020',VOLSER=DOSRES,CPUID=005366A88561
BG 0000 0J01I IPL=$IPLESA ,JCL=$$JCL
BG 0000 $$A$SUPI,VSIZE=512M,VIO=512K,VPOOL=64K,LOG,IODEV=1024
BG 0000 0I30I DATE=07/09/2020,CLOCK=14/01/45,ZONE=EAST/00/00
BG 0000 THE DATE VALUE FORMAT IS MM/DD/YYYY
BG 0000 0J87I RECOVERY BOOST IS ACTIVE
...
Requesting a shutdown boost
The z/VSE system does not provide a shutdown command/procedure. Therefore you need to request a temporary shutdown boost using the SYSDEF SYSTEM AR/JCC/JCS command with the BOOST=START parameter. A shutdown boost lasts up to 30 minutes and can only be requested once per uptime.
Following is an example how to request a shutdown boost using the AR command on the console:
SYSDEF SYSTEM,BOOST=START
AR 0015 1YS5I RECOVERY BOOST STARTED
AR 0015 1I40I READY
You can also request a shutdown boost using the JCC/JCS command from a job running in partition BG:
// SYSDEF SYSTEM,BOOST=START
If a shutdown boost has already been used during the current system uptime the SYSDEF SYSTEM command fails with the following message:
SYSDEF SYSTEM,BOOST=START
AR 0015 1YS5I RECOVERY BOOST FAILED BECAUSE BOOST ALREADY USED
AR 0015 1I40I READY
If the processor (CEC) does not support System Recovery Boost the SYSDEF SYSTEM command fails with the following message:
SYSDEF SYSTEM,BOOST=START
AR 0015 1YS5I RECOVERY BOOST FAILED BECAUSE FACILITY NOT AVAILABLE
AR 0015 1I40I READY
Stopping an IPL or shutdown boost
The z/VSE system automatically stops an IPL boost after 60 minutes and a shutdown boost after 30 minutes. In that case the system prints the following message on the console:
AR 0026 0P83I RECOVERY BOOST IS NO LONGER ACTIVE
You can stop an active IPL or shutdown boost at any time using the SYSDEF SYSTEM AR/JCC/JCS command with the BOOST=STOP parameter. Following is an example how to stop a boost using the AR command on the console:
SYSDEF SYSTEM,BOOST=STOP
AR 0015 1YS5I RECOVERY BOOST STOPPED
AR 0015 1I40I READY
You can also stop a an active IPL or shutdown boost using the JCC/JCS command from a job running in partition BG or your $0JCL procedure:
// SYSDEF SYSTEM,BOOST=STOP
Checking the boost status
You can check whether a boost is active using either the QUERY SYSTEM AR/JCC/JCS command or the SIR AR command. Both show whether any IPL or shutdown boost is active. When running in LPAR the state of any z/VSE IPL or shutdown boost is reported. When running under z/VM the state of any z/VM IPL or shutdown boost is reported.
The QUERY SYSTEM AR/JCC/JCS command shows whether any boost is active or inactive. Following is a sample QUERY SYSTEM output of a system with an active boost:
QUERY SYSTEM
AR 0015 NUMBER OF TASKS TOTAL LIMIT: 255
AR 0015 OLD SUBTASKS LIMIT: 143 IN USE: 21 MAX. EVER USED: 21
AR 0015 NEW SUBTASKS LIMIT: 0 IN USE: 0 MAX. EVER USED: 0
AR 0015 PARALLEL ACCESS VOLUME (PAV): INACTIVE
AR 0015 HIGH PERFORMANCE FICON (ZHPF): INACTIVE
AR 0015 RECOVERY BOOST: ACTIVE
AR 0015 1I40I READY
The SIR AR command reports RECOVERY BOOST ACTIVE when an IPL or shutdown boost is active. Following is a sample SIR SYS output of a system with an active boost:
SIR SYS
AR 0015 CPUID = 005366A885618000
AR 0015 PROCESSOR = IBM 8561-603 02 (266A802) LPAR = T35VSE2 No. = 0083
AR 0015 CPUs = 0002 (Ded.=0000 Shr.=0002) Cap. = 66%
AR 0015 PROC-MODE = z/Arch(64-BIT) IPL(001) 14:01:57 07/09/2020
AR 0015 SYSTEM = z/VSE 6.2.0 10/05/2017
AR 0015 VSE/AF 9.4.0 DY47832 07/10/2020
AR 0015 VSE/POWER 9.4.0 GA-LEVEL 12/01/2017
AR 0015 IPL-PROC = $IPLESA JCL-PROC = $$JCL
AR 0015 SUPVR = $$A$SUPI TURBO-DISPATCHER (B3) ACTIVE
AR 0015 HARDWARE COMPRESSION ENABLED
AR 0015 RECOVERY BOOST ACTIVE
AR 0015 SEC. MGR. = BASIC SECURITY = ONLINE
Stand-Alone Dump (SADUMP) considerations
For z/VSE Stand-Alone Dump (SADUMP) to benefit from Speed Boost you need to update the Stand-Alone Dump program on your dump devices. Please see the z/VSE Diagnosis Tools manual, chapter The DOSVSDMP Utility, section Creating the Standalone Dump Program for details on how to do so.
How much of an improvement you may see is hard to say; a lot of the work Stand-Alone Dump does involves writing data to disk or tape, and that isn’t impacted by the speed of the CPU.
Please note that z/VSE Stand-Alone Dump (SADUMP) does not print a message on the console whether a IPL boost is active.
Implications when using the REIPL command
Please note that when using the REIPL AR command the processor firmware may reject subsequent Speed Boost requests. Therefore please perform an IPL on the Hardware Management Console (HMC) or Support Element (SE) using the HMC/SE task Load instead.
When running in LPAR and on DASD the REIPL AR command effectively only simulates an IPL. This does not cause a new uptime to be observed by the processor firmware. The firmware then may reject further Speed Boost requests if the internal allowance has been depleted.
In case of a rejected IPL boost request the following message is printed on the console during IPL:
BG 0000 0J87I RECOVERY BOOST FAILED DUE TO A MODEL-DEPENDENT REASON
In case of a rejected shutdown boost request the SYSDEF SYSTEM command fails with the following message:
SYSDEF SYSTEM,BOOST=START
AR 0015 1YS5I RECOVERY BOOST FAILED DUE TO A MODEL-DEPENDENT REASON
AR 0015 1I40I READY
I greatly appreciate your feedback either in the comments or via the z/VSE contact form.
Disclaimer: My posts and opinions are my own.
- According to the IBM Redpaper Introducing IBM Z System Recovery Boost (REDP-5563) Speed Boost does not increase IBM software costs.
- According to the IBM Z Solution for z/OS 2.4 IBM Z System Recovery Boost (IZSB100), section Software License Charge and Chargeback Implications, Speed Boost does not increase your 4-hour rolling average (4HRA).