Question: What is the max file size that SAS software can successfully read.
(without considering hardware limit)

Thanks in advance.

Answer: 
"The maximum size of a SAS data set in a Direct Access Bound Library is limited by the maximum size of the library, which is about 2986 GB on 3390 volumes."

<http://support.sas.com/kb/8/213.html>
Reading from a text file, you are limited by the OS typically. Windows allows 1 million characters wide, for example, although SAS can theoretically handle a lrecl of over that.

In general, if you're asking about observations, you will be disk space limited before you are limited by anything else. I've seen a file created that were denominated in PB (petabytes, or 1 thousand terabytes) when on a compressed volume.