Disk Utilization reach 100%

Hi Experts,

I'm using oracle 805, the SAS external storage use only for database. The external storage capacity is 2Tb and 60% is free. I check disk utilization using ST06 show 90-99, Kb transfered/s : 47,527. Then I check the processes in SM50, there is no heavy process, a lot of free work process. I check the avg. response time in ST03 seems normal, around 600-700 ms.

What make the disk utilization high?

thank you

Hardono