CPU reassignment can fail
or be blocked for several reasons. Because the GCU buries its management actions
in SYSMAN or DCL scripts, it may not always identify and report
the reasons for a reassignment fault. The GCU does perform certain
checks before allowing reassignment actions in order, for example,
to prevent attempts to reassign the primary CPU. Other reasons exist
for reassignment faults that can only be detected by the operating
system or console firmware. For example, if the operating system
detects a fault attempting to reassign a CPU that currently has
process affinity or Fast Path duties, a DCL message is displayed
on both the console and the users terminal.
The Galaxy APIs for reassignment are capable of reporting
most faults to the caller. However, even using the reassignment
services, the console may reject a reassignment because of hardware
platform dependencies not readily visible to the operating system.