When merging the graphs if the type of merge is "overlay" then
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the resulting graph shares common X- axis
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Y axes of two charts are plotted against each other
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Ovelay option is not there in LR
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the contents of 2 charts that share a common X Axis, one above the other
Overlay merge in LoadRunner graphs shares the same X-axis (typically time) and plots multiple data series on top of each other. This allows comparing different metrics or the same metric from different runs on a single timeline. The other options describe different merge types or are incorrect.
An 'overlay' merge in LoadRunner combines two graphs so they share a common X-axis (typically elapsed time), overlaying their data onto a single chart for direct time-aligned comparison. This differs from a 'correlate' merge, which instead plots one graph's Y-axis values against the other's Y-axis values, removing the time dimension entirely.