Canceling Vault Jobs Explanation

Hello all,

I have Netbackup 7.5.0.4 and I'm running every week a vault job that takes all of my full backups from the weekend and duplicate it to tapes.

While the vault job is running can I open the tape library and replace some tapes or its locked?

Another question is, if I cancel the vault job, can I run it again? what will happened? it will only take the images that is not yet vaulted or it will start all again?

Thank you all.