La Memory Depth; Anti-Aliasing - Rigol 2000 Series User Manual

Chapter 4 To Set the Sample System RIGOL
In "Auto" mode, the oscilloscope selects the memory depth automatically according
to the current sample rate. At this point, you can adjust the memory depth indirectly
by rotating HORIZONTAL SCALE to adjust the sample rate.

LA Memory Depth

Press Acquire, you can view the current memory depth of the digital channel in LA
Mem Depth. The LA Memory Depth will change with the memory depth of the
analog channel and cannot be set separately.

Anti-Aliasing

At slower sweep speed, the sample rate is reduced and a dedicated display algorithm
is used to minimize the possibility of aliasing.
Press Acquire  Anti-Aliasing to enable or disable the anti-aliasing function. By
default, anti-aliasing is disabled.
MSO2000A/DS2000A User Guide 4-9