The following storage capacities are reported at the Oracle ASM disk group level:
Usable file size: It is the free storage capacity adjusted for mirroring, which is available for new files to restore the redundancy after a disk failure.
Actual available size: It is the actual storage capacity available for use. ReqMirrFreeSize is not considered when you calculate the actual available size.
Actual used size: It is the actual used storage capacity.