Updating the Time Monotonically
If your network does not use time-providers, and the network systems have been running for some time, you may want to update the time on several systems to match UTC or another external reference. When time-providers are absent from your network, the systems remain closely synchronized, but their clocks may drift away from accepted time standards such as UTC.
Use the dcecp clock set command when you want to modify the time on a server system to make it more accurate. The DTS synchronization process ensures that the new time you supply with the command is propagated to the other network systems. In order to update the system clock to a new time, the new time and inaccuracy you specify for a system must form a smaller interval than the current system interval.
In order to use the clock set command effectively, you must have temporary access to a trusted time reference. Such references can include the time signals that many standards organizations disseminate by radio or telephone. You can also use a clock that you have recently verified as accurate. (See Appendix C for suppliers of UTC time.)
Because it is a manually entered command that is used to modify an absolute time, the clock set command is not useful for small inaccuracy settings. The minimum reliable inaccuracy that you can achieve with the command is approximately 1 second. Human error and processing delays combine to make lower settings unreliable. For example, you enter the command and new time and then begin monitoring the reference. When you perceive that the reference has reached the desired time, you press <Return> to initiate the command. Your perception of the reference mark and your pressing of <Return> do not exactly coincide. Furthermore, once the command is initiated, DTS takes time to interpret and execute the command.
The following example shows how to monotonically update the time on a server system, that is, how to reset the clock and eventually propagate the adjustment throughout the network:
dcecp> clock set 1994-10-07-09:30:15.00I01.00
dcecp>
If your systems require synchronization that is closer than 1 second to a standard such as UTC, consider purchasing one of the time-providers listed in Appendix C. All of the time-providers that are described in the listing compensate for transmission and processing delays, and can provide time references that are accurate to the millisecond level.