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Chapter 4, Xgig TraceControl Capture Configuration Segment Capture Options
140 Xgig Analyzer User’s Guide
Start Capture on Selected Segment
This capture mode uses the current segment for capture. Once the segment is full, the capture
stops. This is the default mode. Note that starting a second capture in this mode will overwrite the
data from the first capture in this same segment.
Start Capture on Next Segment
This capture mode works similar to the mode above, but advances the capture to the next segment
before starting capture. Once the segment is full, the capture will wrap within the segment or stop,
depending on the trigger mode. Note that starting a capture after all segments are full will
overwrite capture data, starting with the first segment used for capture.
Start Capture on All Segments from Selected to Last
This capture mode captures in the current segment, and the capture will wrap within the segment
until the capture is stopped. After capture is stopped in this segment, TraceControl will
automatically switch to the next segment and start a capture again and wait to be stopped. This
sequence of captures ends when the last segment has stopped or when the user clicks on the
Stop
button. Note that starting a capture in this mode will overwrite any data in all segments from the
current segment to the last segment.
Note that the Start Capture on All Segments from Selected to Last mode is not valid when you
are in a trigger mode that requires the stop button to be pushed (
Stop When Stop Button is
Clicked (No trigger) . For this condition, the capture is started in the selected segment and you
MUST click the
Stop
button to stop the capture, and the
Stop
button will also stop the sequence of
captures. If you select one of this invalid combination, a message will appear to notify you that the
configuration must be changed.
Examples of Using Segmented Capture Buffer
The examples below will help you see some of uses and advantages of segmenting the capture
buffer.
Tracking a Frequent but Intermittent Drive Error
Assume you need to capture all instances of a SCSI Check Condition that occur over time. For
instance, a drive may be reporting Medium Errors or Recovered Errors and you want to track
down the exact I/O stream and LBA location that caused each one of them. The segmented buffer
allows these instances to be captured back-to-back without missing critical events between
captures. Without the Segmented Capture Buffer feature, you would need to capture/save/repeat in
a script. The time required to save and re-start capture can miss critical instances of the trigger;
having segmented buffers absolutely minimizes the time between trigger and re-start capture.
For this application, you might use the
Start Capture on All Segments from Selected to Last
mode and divide the capture buffer into many segments.