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Segment Capture Options Chapter 4, Xgig TraceControl Capture Configuration
Xgig Analyzer User’s Guide 141
Debugging an Intermittent Loss of Sync
As another example, it may be difficult to track down the cause of a SAS/SATA device losing sync
(LOS error), especially if such a problem happens infrequently for unexplained reasons. You
would likely walk in after a few hours, see that the LOS error had occurred, and the entire trace
buffer would be filled with errors. Your first action would probably be to set a trigger for coding
and disparity errors to see all the events that led us to the LOS; however, there are also several
conditions where a coding/disparity error might cause a LOS, yet these events would not be
relevant to your analysis. These errors might happen at rare instances for a variety of reasons, and
the system can recover from them by retransmitting the frame – these are not the LOS error you
are looking for. You might spend hours taking a trace, only to see later that the error captured has
nothing to do with the LOS issue you are trying to correct.
One way to work towards finding the LOS issue would be to segment the buffer. Now you can
automatically take several traces over a prolonged period of time for coding/disparity errors. If one
of the traces does not demonstrate the LOS condition you are looking for, the next trace on a
separate segment might.
Issues that Have Several Symptoms or Several Possible Diagnoses
Sometimes a particular issue seems to have several symptoms, or you might have several
hypotheses on its cause based on the result of several unique occurrences. If the error happens
infrequently, you can take several traces automatically and see if the events leading up to the error
are the same for each instance of the error.
Compare and Contrast Like Events
For example, you may have a problem where a reset event happens at unexpected times. You could
segment the buffer to take multiple traces, and capture instances of both scheduled and
unscheduled resets. You could then easily compare the different resets within the TraceView
decode display.