The minservers Attribute

The default and minimum recommended value for the minservers attribute is 3; your system requires values from three servers in order to compute a reliable new time. Depending on whether it is a server or clerk, the system has different requirements of the other systems in the network:

· A clerk requires values from three servers.

· A server requires values from two other servers. Each server uses its own clock value when computing a new time.

To reset the minservers attribute value, enter the dts modify command with the -change option to set the desired value. The command accepts values from 1 to 10. For example, to increase the required number of servers to 4, issue the following command:

dcecp> dts modify -change {minservers 4}
dcecp>

Although there is no direct relationship between the localservers attribute, which specifies the number of local servers in a LAN, and the minservers attribute, the minservers attribute value is usually a subset of all the local servers. To see the current values of both or either of these attributes, you can use the dts show command. Wait until the DTS nodes on your LAN are running for at least 10 minutes, before issuing the command. That way, the dts show command is sure to show all of the local servers in your node's synchronization list. The dts show command can be entered with options (-attributes or -all) or without any options, as follows:

dcecp> dts show

{checkinterval +0-01:30:00.000I-----}

{epoch 0}

{tolerance +0-00:10:00.000I-----}

{tdf -0-05:00:00.000I-----}

{maxinaccuracy +0-00:00:00.100I-----}

{minservers 4}

{queryattempts 3}

{localtimeout +0-00:00:05.000I-----}

{globaltimeout +0-00:00:15.000I-----}

{syncinterval +0-00:02:00.000I-----}

{type server}

{courierrole backup}

{actcourierrole courier}

{clockadjrate 10000000 nsec/sec}

{maxdriftrate 1000000 nsec/sec}

{clockresolution 10000000 nsec}

{version V1.0.1}

{timerep V1.0.0}

{provider no}

{autotdfchange no}

{nexttdfchange 1994-10-30-06:00:00.000+00:00I0.000}

{serverprincipal hosts/gumby/self}

{serverentry hosts/gumby/dts-entity}

{servergroup subsys/dce/dts-servers}

{status enabled}

{uuid 000013ed-000b-0000-b8ef-03a4fcdf00a4}

dcecp>

In the previous example, the minservers attribute value is set to 4. This setting provides redundancy; in the case where there are no global servers in the network, the system synchronizes even if a local server becomes unavailable.

Whenever the system cannot contact the number of servers specified by the minservers attribute setting, the system increments the tofewservers counter, logs the event, and displays the event message Too Few Servers Detected. Information included in the event message shows the number of servers that are currently available and the number required. If you see this event message displayed, check whether any of the servers have failed, test the communications links to ensure that the system has not been isolated from the servers, or add servers to the network.

You can use the minservers attribute in other ways, depending on your network configuration. Consider the following cases:

· If you have only a few systems in your network and you want to synchronize the nodes regardless of server drift, lower the minservers attribute value to 1 or 2. Although the resulting synchronized time is a less reliable measure of UTC, you increase the likelihood that the systems will synchronize. If the setting is less than 3, however, the system cannot identify faulty servers. Subsequent server clock drift causes divergence from UTC.

· To increase fault tolerance and ensure that the systems compute reliable times, set the minservers attribute value to 3 (the default setting) or higher. The systems can then identify faulty servers and compute the narrowest overlapping interval for the time values that they receive. Remember, however, that your system will not synchronize until there are at least three servers available.

The number of nodes in your network and the types of applications that you use determine whether guaranteed synchronization or reliable times and fault tolerance are more important.