OSF DCE Administration Guide--Core Components

OSF DCE Administration Guide—Core Components
The maxinaccuracy and syncinterval attributes are interdependent; system
synchronization occurs automatically when both of the following conditions are met:
• The inaccuracy of its clock equals or exceeds the maxinaccuracy attribute value.
• The time since the last synchronization equals or exceeds the syncinterval attribute
value (slightly randomized).
Note that, if the system reaches the syncinterval attribute setting but has not yet reached
the maxinaccuracy attribute setting, the system does not synchronize.
The default syncinterval attribute value is 2 minutes for servers and 10 minutes for
clerks. If you are trying to minimize the skew between systems, you can lower the
syncinterval attribute value. For example, if you want a clerk to synchronize every 5
minutes if its inaccuracy reaches 100 milliseconds, enter the following command:
dcecp> dts modify -change {syncinterval 00-00:05:00.0000}
The syncinterval attribute does not prevent the clock synchronize command from
working. You can synchronize a system at any time by entering this command. The
syncinterval attribute only affects automatic synchronizations triggered by the
maxinaccuracy attribute. (See the clock(8dce) reference page for more information.)
25.5.6 The tolerance Attribute
The tolerance attribute determines how DTS reacts if the system clock becomes faulty.
A faulty clock is a rare condition, but some causes of faulty clocks include the following:
• Defects in the clock hardware, including clock drift that is greater than the
manufacturer’s specifications.
• Malfunctioning time-providers.
• Hardware clock ticks are lost by the operating system.
• The system memory containing the clock value is corrupted.
During the synchronization process, DTS detects that a system’s clock is faulty if the
clock value and its inaccuracy fail to intersect with those of the servers used for
synchronization. This process is shown in Figure 25-2, where value t2 is faulty.
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