Memory allocation is typically handled automatically by the DAQmx driver. Refer to
DAQmx Buffer Size Allocation for Finite or Continuous Acquisitions for more information.
You can manually override NI-DAQmx's choice of buffer size by calling the DAQmx Buffer functions. These functions override the automatic buffer allocation that NI-DAQmx performs. The DAQmx Buffer property node allocates the acquisition buffer based on its input parameter
bufferSize, which is specified in terms of the number of samples the buffer can hold for each channel in the task.
The code below shows a common way of adding the DAQmx Buffer functions into a DAQmx task code. The buffer needs to be manually overridden before the task starts so it is common to place it after the virtual channel is configured but before the task starts.
In C DAQmxCfgInputBuffer (taskHandle, bufferSize);
In C# myTask.Stream.Buffer.InputBufferSize=bufferSize;
Additional Information