This is done for a reason. Pls check this Bugs online for the same.
If you wish you can turn on the cpu monitor as explained below.
Operations Manager console generates an event: "CPU Too Busy events" in the absence of any other issue
Operations Manager console generates many "CPU Too Busy" alerts when the CPU
utilization in the storage system reaches the threshold (configured using
option cpuTooBusyThreshold). High CPU utilization alerts may be considered as
normal in absence of other alerts, as during periods of low user I/O, CPU cycles
are used for background processes. In such cases, you must disable the CPU
monitoring feature to avoid generating "CPU Too Busy" events.
Enter the following command to disable the monitor:
#dfm option set cpumoninterval=off
CPU usage can be tracked through performance counters collected by Performance
Adviser. Use the CPU Utilization graph in "Storage System Summary View" to track
the CPU utilization trend.
From 5.2 the CPU monitor is disabled by default, the monitor can be enabled by
running following command:
# dfm option set cpumoninterval=