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Az alabbi infot a "DIGITAL TPC/IP Services for OpenVMS management" cimu alkotasbol olloztam ki.

 

10.1.3 How the OpenVMS System Maintains the System Clock

The OpenVMS system clock is maintained as a software timer with a resolution of 100 nanoseconds, updated at 10 millisecond intervals. A clock update is triggered when a register, loaded with a predefined value, has decremented to zero. Upon reaching zero, an interrupt is triggered that reloads the register, thus repeating the process.

The smaller the value loaded into this register, the more quickly it reaches zero and triggers an update. The clock runs more quickly in such an instance. A larger value means more time between updates; therefore, the clock runs more slowly.

10.1.4 How NTP Makes Adjustments to System Time

Once NTP has selected a suitable synchronization source, NTP compares the source's time with that of the local clock. If NTP determines that the local clock is running ahead of or behind the synchronization source, NTP uses a general drift mechanism to slow down or speed up the clock as needed. NTP accomplishes this by issuing a series of new ticks. For example, if NTP detects that the local clock is drifting ahead by +0.1884338 second, it issues a series of new ticks in an effort to reduce the difference between the synchronization source and the local clock.

NTP maintains a record of the resets it makes along with informational messages in the NTP log file, TCPIP$NTP.LOG. See Section 10.5 for more details about event logging and help in interpreting an NTP log file. 


10.2.2 Valid Configuration Statements and Options

The following are valid NTP configuration statements:

10.2.3 Sample NTP Configuration File

A sample of the NTP configuration template follows: 


#       Copyright (c) Digital Equipment Corporation, 1998 
# 
#                  Example NTP Configuration File 
# 
# Rename this template to TCPIP$NTP.CONF. 
# 
# See the DIGITAL TCP/IP Services for OpenVMS Management manual for 
# additional commands and detailed instructions on using this 
# configuration file. 
# 
# The Network Time Protocol (NTP) provides synchronized timekeeping 
# among  a set of distributed time servers and clients. The local 
# OpenVMS host  maintains an NTP configuration file, TCPIP$NTP.CONF, of 
# participating peers. TCPIP$NTP.CONF is maintained in the 
# SYS$SPECIFIC:[TCPIP$NTP] directory. 
# 
# As the system manager populating this file, you must determine the 
# peer hosts with which the local hosts should negotiate and 
# synchronize.  Include at least one (but preferably three) 
# hosts that you are  certain have the following characteristics: 
# 
#       * provide accurate time 
#       * synchronize to Internet Time Servers (if they are not 
#   themselves Internet Time Servers) 
# 
# The NTP configuration file is not dynamic, and therefore requires 
# restarting NTP  after being edited to make the changes take effect. 
# However, you can make run-time configuration requests interactively 
# using the TCPIP$NTPDC utility. 
 
# Your NTP configuration file should always include the following 
# driftfile entry.  The driftfile is the name of the file that stores 
# the clock drift (also known as frequency error) of the system clock. 
 
 
driftfile SYS$SPECIFIC:[TCPIP$NTP]TCPIP$NTP.DRIFT 
 
# Sample peer entries follow.  Replace them with your own list of 
# hosts and identify the appropriate association mode.  If you 
# specify multiple hosts, NTP can choose the best source with which to 
# synchronize. This also provides reliability in case one of the hosts 
# becomes unavailable. 
 
 
# Identify each peer with a DNS host name or with an IP address 
# in dotted-quad notation. 
 
peer 18.72.0.3 
peer 130.43.2.2 
peer 16.1.0.22 
peer parrot 
 
# The following commands let you use NTP with 
# another time service  such as DTSS.  If enabled (by removing #), 
# NTP will not set the system clock. 
 
# server 127.127.1.0 prefer 
# fudge 127.127.1.0 stratum 0

 

 

Emil