The dup call does not alter the inode or any system table. It only alters the file descriptor table which is a process related table.
I think these 2 questions might help you understand what dup actually does. Difference between creating a duplicate file descriptor using dup() and creating a hard link? dup2 / dup - why would I need to duplicate a file descriptor?
Bottom-line : Dup doesn't affect the system in anyway , just the process.