User`s guide

Remarks
This command differs from the DATA:REMove? command in that R? will
read and erase whatever readings are available in memory, up to the
specified <max_count>. On the other hand, DATA:REMove will error if the
requested number of readings are not in memory when the command is
sent. You can read memory at any time using the R? command, even
during a measurement.
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 (Mem Ovfl) 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 mainframe power is cycled, when the configuration is
changed (see CONFigure), or on an INITiate command.