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Timekeeping, Drifting, System Clock Accuracy?

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The Question is:

I have an AlphaServer ES45 Model 1B which is gaining time of 2-3 seconds/day.
 We are running a high availability application which doesn't like time going
 backwards so it is difficult to rectify. Over a 6 month period the clock ran
 about 7 minutes fast.
 Anything I've found about clock drift mentions systems losing time.
Two questions : Is there anything I can do to correct the issue without
 affecting my application? What is considered normal or acceptable for the
 system clock, we haven't seen it on any other Alpha (5).

The Answer is :

  This and other timekeeping-related matters are discussed within the
  OpenVMS Frequently Asked Questions (FAQ) documentation -- you will
  want to link to an external time-base, and various options are
  available.  The FAQ also has details around the hardware and
  software clocks, and around the relative accuracy expected.
  There are two topics refered to as clock drift, one involves
  lost or gained time with the most common being lost -- see the
  FAQ for this -- and the other variation of the topic involves
  using drifting to correct the system time.  Available tools
  do drift the time to correct inaccuracies, but for obvious
  reasons these mechanisms will slow or speed the system clock
  updates but will not cause the system time to be set back.

answer written or last revised on ( 20-APR-2004 )

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