High system CPU usage during query run

Hello,

 

I have a problem with my database that I cannot fugure out. We have queries running on the server and we observe that the sytem CPU% usage goes to 97 - 98% and the quries take tremendous amount of time to finish. On other days the queries would run quick and the system CPU usage percentage is low.

 

We have done disk scans and did not find issue as per the sys admin. What from the database perspective I should investigate to resolve the issue?

 

Our server has dual core Intel Xeon processors 2.66 GHZ, 16GB RAM and RAID10 1.5 TB.

 

Please I need advise on this problem.

 

Thanks

Abu