Each DAS or SAN disk must have a partition table. Oracle recommends creating exactly one partition for each disk containing the entire disk. Use Microsoft Computer Management or the command-line tool diskpart to create the partition. Once the partitions have been created, run asmtoolg or asmtool. These tools associate meaningful, persistent names with disks to facilitate using those disks with Oracle Automatic Storage Management. Oracle Automatic Storage Management uses disk strings to more easily operate on groups of disks at once, so the names created by asmtool make this easier than using Windows drive letters. All disk names created by asmtool begin with the prefix ORCLDISK for identification purposes.

Oracle Automatic Storage Management uses the value of initialization parameter ASM_DISKSTRING as its search path when it discovers disks. The default value of ASM_DISKSTRING is \\.\ORCLDISKn. If you want a different search path, then you must specify a different value for this parameter.