The PHY_IO privilege lets the user's process
execute the Queue I/O Request ($QIO) system service to perform physical-level
I/O operations.
Usually, process I/O requests are handled indirectly
by use of an I/O package such as OpenVMS Record Management Services
(RMS). However, to increase their control over I/O operations and
to improve the efficiency of their applications, skilled users sometimes
prefer to handle directly the interface between their process and
a system I/O driver program. They can do this by executing the $QIO
system service; in many instances, the operation called for is a physical-level
I/O operation.
Grant the PHY_IO privilege only to users who need
it; grant this privilege even more carefully than the LOG_IO privilege.
If this privilege is given to unqualified users who have no need for
it, the operating system and service to other users can be easily
disrupted. Such disruptions can include the destruction of information
on the system device, the destruction of user data, and the exposure
of confidential information.
The PHY_IO privilege also lets a process perform
the following tasks:
Task
Interface
Access
an individual shadow-set member unit
$ASSIGN, $QIO
Create
or delete a watchpoint
$QIO request to the SMP watchpoint driver (WPDRIVER)
Map
an LTA device to a server/port (IO$_TTY_PORT!IO$M_LT_MAPPORT)
$QIO request to a LAT
port driver (LTDRIVER)
Issue
the following I/O requests:
Logical I/O request
Logical or virtual I/O request with IO$M_MSCPMODIFS
modifier
Physical I/O to private, non-file-structured device
$QIO
Modify
the following terminal attributes: HANGUP SET_SPEED SECURE_SERVER
SET TERMINAL or the terminal
driver (TTDRIVER) /[NO]HANGUP /[NO]SET_SPEED /[NO]SECURE_SERVER
Issue
IO$_ACCESS (diagnostic) function to DEBNA/NI device driver
$QIO request to a synchronous
communications line (XGDRIVER)
Enable
Ethernet promiscuous mode listening
Issue IO$_ACCESS
(diagnostic) function to Ethernet common driver
