Switch between Auto and On-Demand Sampling ($)
This option switches the sampling interval between automatic and on-demand and the current value is visible in the upper-left corner of the ProTop RT screen.
"Automatic" sets sampling interval per interval rate. Used in conjunction with the option to look at the default option interval rate of change as opposed to the cumulative change (since ProTop started) or the raw numbers (since the database server started)
"On-demand" sets sampling rate to the interval between user keystrokes of the space bar.