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$_DEVCHAR2.
Disk Device Characteristics lists the possible characteristics for disk devices.
Dual-path device with two
unit control blocks (UCBs).
DEV$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).