Specifications

Data Structures
1.19 Unit Control Block (UCB)
Table 1–22 (Cont.) Contents of Unit Control Block
Field Name Contents
DEV$V_OPR Operator device
DEV$V_RCT Device contains RCT
DEV$V_NET Network device
DEV$V_FOD File-oriented device (disk and magnetic tape, for
example)
DEV$V_DUA Dual-ported device
DEV$V_SHR Shareable device (used by more than one program
simultaneously)
DEV$V_GEN Generic device
DEV$V_AVL Device available for use
DEV$V_MNT Device mounted
DEV$V_MBX Mailbox device
DEV$V_DMT Device marked for dismount
DEV$V_ELG Error logging enabled
DEV$V_ALL Device allocated
DEV$V_FOR Device mounted as foreign (not file structured)
DEV$V_SWL Device software write-locked
DEV$V_IDV Device capable of providing input
DEV$V_ODV Device capable of providing output
DEV$V_RND Device allowing random access
DEV$V_RTM Real-time device
DEV$V_RCK Read-checking enabled
DEV$V_WCK Write-checking enabled
UCB$L_DEVCHAR2 Second longword of device characteristics. The DPT of every driver should
specify symbolic constant values (defined by the $DEVDEF macro in
SYS$LIBRARY:STARLET.MLB) for this field. The driver-loading procedure
writes the field when the procedure creates the UCB.
The system defines the following device characteristics:
DEV$V_CLU Device available clusterwide
DEV$V_DET Detached terminal
DEV$V_RTT Remote-terminal UCB extension
DEV$V_CDP Dual-pathed device with two UCBs
DEV$V_2P Two paths known to device
DEV$V_MSCP Disk or tape accessed using MSCP
DEV$V_SSM Shadow set member
DEV$V_SRV Served by MSCP server
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