User`s guide

Remarks
Sending the READ? command is similar to sending the INITiate command
followed immediately by the FETCh? command.
The 34410A provides volatile reading memory for up to 50,000 readings.
The 34411A/L4411A provides volatile reading memory for up to 1,000,000
readings. If memory overflows, the new readings will overwrite the first
(oldest) readings stored; the most recent readings are always preserved.
In addition, bit 14 is set in the Questionable Data Register's condition
register (see Status System Introduction).
The instrument clears all readings from volatile memory after a Factory
Reset (*RST command), after an Instrument Preset (SYSTem:PRESet
command), when the power is cycled, when the configuration is changed
(see CONFigure), or on an INITiate command.