UC Davis SNMP MIB states the following for ssCpuRawSystem:
ssCpuRawSystem: This object may sometimes be implemented as the combination of the 'ssCpuRawWait(54)' and 'ssCpuRawKernel(55)' counters, so care must be taken when summing the overall raw counters.
There's a great summary of the CPU objects in opennms community and it looks like they have also encountered this, but the question is still open.
How can I determine what ssCpuRawSystem implements in my system?
As an example, lets take the following S/W example: Linux, kernel 2.6.32 + net-snmp version 5.2.0.
The text in that message is simply a warning that on some systems the exact values may not be available and thus the best thing the Net-SNMP software could do is to combine the other results.
To figure out exactly what is being done, the right thing to do is always to look at the source code (in agent/mibgroup/ucd-snmp/vmstat_linux.c for linux, but will be a different parallel file for other architectures).
This shows:
case CPURAWSYSTEM:
long_ret = (vmstat(cpurawsystem)+vmstat(cpurawinter)+vmstat(cpurawsoft)) & MAX_COUNTER;
return ((u_char *) (&long_ret));