How can I be sure my VHS is not going to erase while I record it to DVD?

I need to copy the VHS of my wedding tape to DVD-R on a TV/VHS/DVD combination. I am terrified that my VHS tape will erase while it's recording onto the DVD, and if for some reason the recording doesn't work, I will no longer have my wedding tape! My VHS tape has the black square hole removed on the back. Does that mean the VHS tape CANNOT be erased? HELP!