甲骨文怎么删除子网啊？

Are you sure you want to terminate the Subnet 公共子网?
The Subnet ocid1.subnet.oc1.ap-seoul-1.a references the VNIC ocid1.vnic.oc1.ap-seoul-1a. You must remove the reference to proceed with this operation.

我该如何在实例种解绑VNIC呢？