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Disk Driver Device Information  



You can obtain information on all disk device characteristics by using the Get Device/Volume Information ($GETDVI) system service (refer to the HP OpenVMS System Services Reference Manual).

$GETDVI returns disk characteristics when you specify the item codes DVI$_DEVCHAR and DVI$_DEVCHAR2. Disk Device Characteristics lists the possible characteristics for disk devices.

Table 4   Disk Device Characteristics
Characteristic1 Meaning

Dynamic Bits (Conditionally Set)
DEV$M_AVL
Device is on line and available.
DEV$M_CDP2 3
Dual-path device with two unit control blocks (UCBs).
DEV$M_CLU
Device is available clusterwide.
DEV$M_2P
Device is dual-pathed.
DEV$M_FOR
Device is foreign.
DEV$M_MNT
Volume is mounted.
DEV$M_RCK
Perform data check on all reads.
DEV$M_WCK
Perform data check on all writes.
DEV$M_MSCP
Device is accessed using the mass storage control protocol.
DEV$M_RCT
Disk contains replacement and caching table.
DEV$M_SRV
For a cluster, device is served by the MSCP server.

Static Bits (Always Set)
DEV$M_FOD
Device is file-oriented.
DEV$M_IDV
Device is capable of input.
DEV$M_ODV
Device is capable of output.
DEV$M_RND
Device is capable of random access.
DEV$M_SHR
Device is shareable.

DVI$_DEVBUFSIZ returns the buffer size. The buffer size is the default to be used for disk transfers (this default is normally 512 bytes). DVI$_DEVTYPE and DVI$_DEVCLASS return the device type and class names, which are defined by the $DCDEF macro. The disk model determines the device type. For example, the device type for the RA81 is DT$_RA81. (Foreign device types take the form DT$_FD1 through DT$_FD8.) The device class for disks is DC$_DISK.

DVI$_CYLINDERS returns the number of cylinders per volume (that is, per disk), DVI$_TRACKS returns the number of tracks per cylinder, and DVI$_SECTORS returns the number of sectors per track. Values are returned as 4-byte decimal numbers.

DVI$_MAXBLOCK returns the maximum number of blocks (1 block = 512 bytes) that can be contained on the volume (that is, on the disk). Values are returned as 4-byte decimal numbers. This information can be used, for example, to determine the density of an RX02 diskette (single density = 494 blocks, double density = 988 blocks).


Footnotes
1Defined by the $DEVDEF macro.
2These bits are located in DVI$_DEVCHAR2.
3MASSBUS only.

( Number takes you back )


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