Input >> Buffer Size

NI-DAQmx C Properties

Input >> Buffer Size

Data Type: uInt32
Description: Specifies the number of samples the input buffer can hold for each channel in the task. Zero indicates to allocate no buffer. Use a buffer size of 0 to perform a hardware-timed operation without using a buffer. Setting this property overrides the automatic input buffer allocation that NI-DAQmx performs.

You can get/set/reset this property using:
  DAQmxGetBufInputBufSize
  DAQmxSetBufInputBufSize
  DAQmxResetBufInputBufSize