Well - you only have two options: either make the field it's going into bigger (right way), or make what is to go into to it smaller (not the right way). If you really think you need to shorten the input instead of lengthening the output, then use string manipulation functions to pick some part of the field you want. That's LEFT, RIGHT or SUBSTRING, depending on what applies to your scenario.

Unless you know for a fact that there's garbage in the last 15 characters, it seems a strange choice to just truncate. You're screwing up your data.

And since you want to do it at the "database level" and not the SP level - then expanding the field is the solution. I don't know of a "ignore truncation errors" setting, and I don't think 2000 just ignores the error. That certainly doesn't ring true with my past experience.