Specifications

Data Structures
1.19 Unit Control Block (UCB)
Table 1–22 (Cont.) Contents of Unit Control Block
Field Name Contents
UCB$V_UNLOAD Unload volume at dismount.
UCB$V_TEMPLATE Template UCB from which other UCBs for
this device are made. The $ASSIGN system
service checks this bit in the requested UCB
and, if the bit is set, creates a UCB from the
template. The new UCB is assigned instead.
UCB$V_MNTVERIP Mount verification in progress.
UCB$V_WRONGVOL Volume name does not match name in the
VCB.
UCB$V_DELETEUCB Delete this UCB when the value in UCB$W_
REFC becomes zero.
UCB$V_LCL_VALID The volume on this device is valid on the local
node.
UCB$V_SUPMVMSG Suppress mount-verification messages if they
indicate success.
UCB$V_MNTVERPND Mount verification is pending on the device
and the device is busy.
UCB$V_DISMOUNT Dismount in progress.
UCB$V_CLUTRAN VAXcluster state transition in progress.
UCB$V_WRTLOCKMV Write-locked mount verification in progress.
UCB$V_SVPN_END Last byte used from page is mapped by a
system virtual page number.
UCB$V_ALTBSY Unit is busy via an alternate startup path.
UCB$V_SNAPSHOT Restart validation is in progress.
UCB$W_DEVSTS Device-dependent status. Read and written by device drivers.
The system defines the following status bits:
UCB$V_JOB Job controller has been notified.
UCB$V_TEMPL_BSY Template UCB is busy.
UCB$V_PRMMBX Device is a permanent mailbox.
UCB$V_DELMBX Mailbox is marked for deletion.
UCB$V_SHMMBS Device is shared-memory mailbox.
Disk drivers use bits in UCB$W_DEVSTS as follows:
UCB$V_ECC ECC correction made.
UCB$V_DIAGBUF Diagnostic buffer is specified.
UCB$V_NOCNVRT No logical block number to media address
conversion.
UCB$V_DX_WRITE Console floppy write operation.
UCB$V_DATACACHE Data blocks are being cached.
UCB$W_QLEN* Length of pending-I/O queue (pointed to by UCB$L_IOQFL).
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