Technical data

Managing Peripheral Devices
8.5 Automatically Configuring Devices for OpenVMS Alpha Systems
Prior to OpenVMS Alpha Version 7.1, configuration tables were built
into the OpenVMS kernel and could not be modified without replacing a
system image. As of OpenVMS Alpha Version 7.1, the configuration tables
are constructed from ASCII text files on the system disk. A system file
(SYS$SYSTEM:SYS$CONFIG.DAT) is provided for all OpenVMS supported
devices, and a user file (SYS$SYSTEM:SYS$USER_CONFIG.DAT) is provided
for all third-party, layered-product, and user-written device drivers. The system
reads these files during the boot process and uses the files to create a set of
configuration tables. These tables are used for subsequent autoconfiguration of
hardware devices. Although the tables are built from two files and collected by
bus type, they can be considered one logical configuration table of known devices.
Section 8.5.2 describes how to use the SYS$SYSTEM:SYS$USER_CONFIG.DAT
file to autoconfigure devices.
8.5.2 Using File-Based Autoconfiguration
File-based autoconfiguration reads two files during system boot to build the
configuration tables of known devices:
SYS$SYSTEM:SYS$USER_CONFIG.DAT
SYS$SYSTEM:SYS$CONFIG.DAT
Both files use the same format, and the data from both files are combined to
create the configuration tables for each bus on the system. The SYS$USER_
CONFIG.DAT file is read first, and takes precedence over any duplicate device
descriptions contained in both files. If multiple device descriptions exist in a
single file, the first occurrence of the description is used.
The configuration files consist of device description blocks, each of which provides
the information needed to configure the correct device driver for a device.
Each device description block consists of a series of statements starting with a
DEVICE keyword and ending with the END_DEVICE keyword. Between these
two keywords, additional keywords define the hardware ID, the device name, the
driver name, the bus type, and any other required or optional information.
The SYS$USER_CONFIG.DAT file is an ASCII text file, which can be processed
with any utility that handles variable-length record files (for example, a text
editor or DCL commands).
Note
The SYS$CONFIG.DAT file is read-only and should not be modified by
users or by third parties. It should only be modified by Compaq, and it
might be replaced by OpenVMS upgrades. Inappropriate edits to this file
could result in the inability to boot the system.
8.5.2.1 Adding Descriptions to SYS$USER_CONFIG.DAT
Statements in the SYS$SYSTEM:SYS$USER_CONFIG.DAT take the general
form:
KEYWORD = value
8–12 Managing Peripheral Devices