The LOG_IO privilege lets the user's process execute the QueueI/O Request ($QIO) system service to perform logical-level I/O operations.LOG_IO privilege is also required for certain device control functions,such as setting permanent terminal characteristics. A process withthe typical privileges of NETMBX and TMPMBX that also holds LOG_IOand SYSNAM can reconfigure the Ethernet using the Phase IV network configurationprocedure, NICONFIG.COM.
Usually, process I/O requests are handled indirectly by useof an I/O package such as OpenVMS Record Management Services (RMS).However, to increase their control over I/O operations and to improvethe efficiency of I/O operations, skilled users sometimes preferto handle the interface between their process and a system I/O driverprogram directly. They can do this by executing $QIO; in many instances,the operation called for is a logical-level I/O operation. Notethat logical level functions are permitted without LOG_IO privilegeon a device mounted with the /FOREIGN qualifier and on non-file-structureddevices.
Grant this privilege only to users who need it because itallows a process to access data anywhere on the selected volumewithout the benefit of any file structuring. If this privilege isgiven to unqualified users who have no need for it, the operatingsystem and service to other processes can be easily disrupted. Such disruptionscan include the destruction of information on the system device,the destruction of user data, and the exposure of confidential information.
The LOG_IO privilege also lets a process perform the followingtasks:
Task
Interface
Issue physicalI/O calls to a private, non-file-structured device
$QIO
Modify the following terminalattributes: HANGUP SET_SPEED SECURE_SERVER
SET TERMINAL (or TTDRIVER) /[NO]HANGUP /[NO]SET_SPEED /[NO]SECURE_SERVER
HP OpenVMS Guide to System Security
Security for the System Administrator
