Creating DAS or SAN Disk Partitions for Oracle Automatic Storage Management
You can use direct-attached storage (DAS) and storage area network (SAN) disks with Oracle ASM.
To use a DAS or SAN disk in Oracle ASM, the disk must have a partition table. Oracle recommends creating exactly one partition for each disk.
Note:
You can use any physical disk for Oracle ASM, if it is partitioned.