Convert it to CSV is the fastest method. You can do that manually or there's a script on here somewhere that can automate that if necessary. It's VBS though, so you would need permissions to run it.
Is it an actual ERROR or a WARNING that a name has been truncated? There is a difference. SAS has a limit of 32 characters for a variable name. If your source file has more than 32 characters SAS has to do something which may involve truncating a name or if you have multiple variables with the same leading 32 (+) characters you may get a name of VAR plus the column number.
Upon re-reading, your subject doesn't match your actual question. Or are you having both issues? The 256 limit depends on the engine being used (DBMS) and the xx too long, is the SAS limitation of 32 characters. That's usually a note that it will convert it though.