In certain situations, the HP-UX operating system may assign the CPU to high priority interrupts or other higher priority processes like HAD. In this scenario, HAD cannot function until it gets scheduled. To overcome this issue, VCS provide the option of running HAD on a specific processor. This way you can shield HAD from other high priority processes.
See System attributes.
To modify the CPUBinding attribute
hasys -modify sys1 CPUBinding BindTo CPUNUM|NONE|ANY [CPUNum number]