Abstract: Key space analysis is provided to improve the merge phase of a sorting process or a computer merge operation where strings of records or files of presorted records are to be merged in order of a key. Key spaces are identified as strings or groups of strings, files or groups of files, whose range of entries does not overlap the range of entries of another key space. The strings or files within each key space are then combined and/or merged, as needed, independently of strings or files in other key spaces, and written directly to the output destination.