Tips for modifying and downloading an FB online

Hello Experts!

Can I ask for a tips and tricks in modifying and downloading an FB, with multiple instances, without stopping the PLC?

I heard that if you just modify the code of the FB but not the declaration addresses, there's no problem, you can download it online. But how about deleting or adding a declaration address? Can I download it without a stop?

I've heard it can be done, but with a correct sequence/procedure of DB->FB->FC? But I'm somewhat wondering, for if I increase or decrease an FB declaration, and download it before the FC, then the online FC (FB calls, with old addresses) is not in correspondent to the downloaded FB (with less or more addresses)? But the a more obvious problem if I download the new FC (updated FB calls) before the new FB (that which it calls)! This seems to be a dillema!

So please help!

PS:I am currently working on TIA Portal and S7-315 PN/DP, but I would also ask and appreciate any answers, on the same inquiry, for the classic Simatic Step 7.

Thanks for any response!