How to do root cause analysis of KPI’s

Dear Experts

Could you please help to share your experience the steps or documents of root cause analysis or basic analysis of the below CS and HSS core KPI’s :-

HSS KPI’s
Absent SMS Subscriber
Absent Subscriber
Average CPU Usage
Call Barred
Max CPU Load
Number of 2G Subscribers Roaming Outside the Home PLMN Country
Number of EPS Active Subscribers
Number of Sent Response Messages over Cx Interface of HSS
Number of Sent Response Messages over Sh Interface of HSS
Number of Sent Successful Response Messages over Cx Interface of HSS
Number of Sent Successful Response Messages over Sh Interface of HSS
Number of Static EPS Subscribers
Operation Aborted Times
Operation Requests
Operation Timeout Times
Positive Responses
Roaming Not Allowed
Success Rate of Cancel Location
Success Rate of GPRS Location Update
Success Rate of Insert Subscriber Data
Success Rate of Provide Roaming Number
Success Rate of Send Authentication Info
Success Rate of Send Routing Info
Success Rate of Send Routing Info for SM
Success Rate of Update Location
Successful Response Rate of CLR Messages
Successful Response Rate of IDR Messages
System Failure
Unexpected Data Value
Unknown Subscriber
Success Rate of Process Unstructured SS Data (%)
Success Rate of Process Unstructed SS Request(%)
Success Rate of Messages over Sh Interface (%)
Success Rate of Cx Interface Messages (%)

CS core KPI’s
CONNECTED RATIO %
Handover Success Rate%
MAP Standard Operation
CPU load rate(%)
2G Assignment Success Rate
3G Assignment Success Rate
Location update Success Rate
Paging Success Rate
Busy Hour Call Attempts
Global Answer Traffic (Erl)
Global Seizure Traffic (Erl)
3G Call Setup time
2G Call Setup time
A Interface Authentication Success Rate
Answer to Bid Ratio
BSC Trunk Utilization
EC Utilization
Handover Success Rate
MSC CSSR
Packet Loss Rate
SMS Success Rate
TC Utilization
Drop Call rate