What are the differences among fetch, read, and meas in the SCPI programming commands of the Keysight n9030 signal analyzer?

1. What is the difference between fetch, read, and measure programming in the keysight signal analyzer? Simply put, Fetch is to directly read the value of the most recent measurement in the current measurement mode. It is usually used to retrieve data after a measurement has been completed. For example, "FETCh:SAN2?", this instruction will read the data of Trace2 in SA mode. If it is not currently in SA mode, the instruction will return an error. Read will switch to the specified measurement mode, trigger a measurement, and then return the measurement value. For example, "READ:SAN2?", this instruction will switch to SA mode, trigger a scan, and then return the data of Trace2. Measure will immediately stop the current test, then switch to the specified measurement mode in the instruction, and use the factory default parameter settings in this mode, then trigger a measurement and return the measurement value. For example, "MEAS:SAN2?", this instruction will switch to SA mode, use the default parameters, trigger a scan, and then return the data of Trace2.  

2. How to read the data of Trace in channel power mode by programming? What is the command? For example, for n9030B signal analyzer, you can use “FETCh:CHPower2?”, “MEASure:CHPower2?” or “READ:CHPower2?” according to the specific needs.