Physical Disk
A physical disk represents the entire disk and points to the following:
\Device\Harddiskx\Partition0
Windows NT automatically creates a symbolic link name of \\.\PhysicalDrivex, where x is the number corresponding to your hard disk drive number in Disk Administrator and matching the x in \Device\Harddiskx\Partition0. \\.Symbolic link name \PhysicalDrivex is automatically defined by Windows for every hard disk in the computer. For example, a computer with three hard disks:
\\.\PhysicalDrive0
\\.\PhysicalDrive1
\\.\PhysicalDrive2
Internally, these names expand to the following:
\\.\PhysicalDrive0 = \Device\Harddisk0\Partition0
\\.\PhysicalDrive1 =\Device\Harddisk1\Partition0
\\.\PhysicalDrive2 =\Device\Harddisk2\Partition0
Partition0 is special, because it represents the entire physical disk regardless of any partitioning scheme on that disk. On all disks recognized by Windows, Disk Administrator writes a signature on the first block of all disks. To avoid overwriting that block, Oracle9i database skips the first block of a physical raw partition that is used for an Oracle9i datafile.
Logical Partition
A logical partition is a partition created by Disk Administrator that points to a drive other than \Device\Harddiskx\Partition0.
Logical partitions are initially assigned names with drive letters (\\.\drive_letter:) and typically re-assigned symbolic link names (\\.\symbolic link name). For example, \\.\D: may be assigned a symbolic link name of \\.\ACCOUNTING_1. Regardless of whether a drive letter or symbolic link name is used, logical partitions are defined to represent a specific partition in a disk rather than the entire disk. Internally, these names can expand to:
\\.\D:= \Device\Harddisk2\Partition1
\\.\ACCOUNTING_1= \Device\Harddisk3\Partition2
Drive letters can be assigned to specific partitions, using Disk Administrator. Symbolic link names can, on the other hand, be assigned using a utility such as DOSDEV.EXE, which is available with Windows NT Resource Kit.
Physical Disk and Logical Partition Considerations
Consider the following when deciding which raw partition to use:
Physical disks are automatically defined by Windows to represent the entire disk, and should never be defined by the user.
Logical partitions must be defined by the user to represent a specific partition in a disk. These partitions should be logical partitions or drives contained in an extended partition. They should never be defined as Partition0.
Using an entire disk (Partition 0) for an Oracle9i datafile and using a partition that occupies the entire disk for an Oracle9i datafile are not the same thing. Even when a partition occupies the entire disk, there is still a small space on the disk that is not part of the partition.
If you are using an entire disk for an Oracle9i datafile (Partition0), use the pre-defined physical raw names that Windows NT provides.
Use a logical partition if you are using a specific partition and it occupies the entire disk.
If using a specific partition created with Disk Administrator, define and use a symbolic link name rather than a logical partition number (even if it occupies the entire disk).
A physical disk represents the entire disk and points to the following:
\Device\Harddiskx\Partition0
Windows NT automatically creates a symbolic link name of \\.\PhysicalDrivex, where x is the number corresponding to your hard disk drive number in Disk Administrator and matching the x in \Device\Harddiskx\Partition0. \\.Symbolic link name \PhysicalDrivex is automatically defined by Windows for every hard disk in the computer. For example, a computer with three hard disks:
\\.\PhysicalDrive0
\\.\PhysicalDrive1
\\.\PhysicalDrive2
Internally, these names expand to the following:
\\.\PhysicalDrive0 = \Device\Harddisk0\Partition0
\\.\PhysicalDrive1 =\Device\Harddisk1\Partition0
\\.\PhysicalDrive2 =\Device\Harddisk2\Partition0
Partition0 is special, because it represents the entire physical disk regardless of any partitioning scheme on that disk. On all disks recognized by Windows, Disk Administrator writes a signature on the first block of all disks. To avoid overwriting that block, Oracle9i database skips the first block of a physical raw partition that is used for an Oracle9i datafile.
Logical Partition
A logical partition is a partition created by Disk Administrator that points to a drive other than \Device\Harddiskx\Partition0.
Logical partitions are initially assigned names with drive letters (\\.\drive_letter:) and typically re-assigned symbolic link names (\\.\symbolic link name). For example, \\.\D: may be assigned a symbolic link name of \\.\ACCOUNTING_1. Regardless of whether a drive letter or symbolic link name is used, logical partitions are defined to represent a specific partition in a disk rather than the entire disk. Internally, these names can expand to:
\\.\D:= \Device\Harddisk2\Partition1
\\.\ACCOUNTING_1= \Device\Harddisk3\Partition2
Drive letters can be assigned to specific partitions, using Disk Administrator. Symbolic link names can, on the other hand, be assigned using a utility such as DOSDEV.EXE, which is available with Windows NT Resource Kit.
Physical Disk and Logical Partition Considerations
Consider the following when deciding which raw partition to use:
Physical disks are automatically defined by Windows to represent the entire disk, and should never be defined by the user.
Logical partitions must be defined by the user to represent a specific partition in a disk. These partitions should be logical partitions or drives contained in an extended partition. They should never be defined as Partition0.
Using an entire disk (Partition 0) for an Oracle9i datafile and using a partition that occupies the entire disk for an Oracle9i datafile are not the same thing. Even when a partition occupies the entire disk, there is still a small space on the disk that is not part of the partition.
If you are using an entire disk for an Oracle9i datafile (Partition0), use the pre-defined physical raw names that Windows NT provides.
Use a logical partition if you are using a specific partition and it occupies the entire disk.
If using a specific partition created with Disk Administrator, define and use a symbolic link name rather than a logical partition number (even if it occupies the entire disk).
