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Description
General Information
When OpenVMS is used with Fibre Channel disks, it requires a user-defined identifier (UDID) for each Fibre Channel LUN to detect and name the storage device.
A UDID is a non-negative integer that is defined on the storage sub-system and used when an OpenVMS device name is created.
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This article describes the use of the user-defined identifier (UDID) in an OpenVMS environment. Charon products do not specify requirements regarding this value. The requirements are set by the OpenVMS operating system. |
Valid UDID values
Valid UDID values are decimal numbers from 0 to 32766.
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If the Fibre Channel disk device is served via MSCP, the device identifier is limited to 9999. |
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A Fibre Channel storage disk device name is created by the operating system from the constant value $1$DGA and the user-defined device identifier, nnnnn. For example: "$1$DGA512".
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- Historically, DEC reserved the opcode 0xEC to communicate the UDID from a HSG80 to OpenVMS.
- Later, the concept of the UDID was included in the SCSI-3 specification as a variation of IDENTIFYING INFORMATION (A3/05 opcode/subcode). Here, the UDID 0 is not available (i.e., no disk device named $1$DGA0).
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Storage sub-system support for opcode 0xEC is only necessary if Fibre Channel is attached via PCI pass-through and the device $1$DGA0 is required by the OpenVMS guest system |
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. If Fibre Channel is virtualized, Charon provides support for the 0xEC command. |
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