Large TIN surfaces, such as those built from DEM files, can require a substantial amount of memory (RAM and virtual memory) and disk space to build and save the surface. TIN surfaces require about 100 bytes per point, whereas grid surfaces require about 16 bytes per point.
It is important to ensure that you have sufficient resources before you build a surface using a DEM file. Also, be aware that certain commands may take longer than expected when working with these surfaces.
As a general rule, a 1 MB DEM file contains 160,000 points. For larger DEM files, the number of points grows proportionately to the DEM file size at a rate of approximately 160,000 points per 1 MB of DEM file size.