Hyper APAR SO12995 states the problem it corrects can only occur if Simultaneous Multithreading (SMT) is in use, where there are multiple threads per core.
How to determine if SMT is enabled and being used ?
Release : 15.0
Component : SYSVIEW
IBM LOADxx parmlib option PROCVIEW CORE|CPU enables/disables SMT for the life of the IPL • PROCVIEW CORE on z13 enables SMT support • IPL required to switch between PROCVIEW CPU and CORE
Simultaneous multithreading (SMT) allows two active instruction streams per core, each dynamically sharing the core's execution resources. SMT is available on the z13 for workloads running on the IFL and the IBM z Integrated Information Processor (zIIP). SMT is disabled by default.