We have a Cisco 2821 router that will have an IOS upgrade via a new flash chip. If my startup-config contains all the useful information (on NVRAM) about the interfaces, do I really need to keep the vlan.dat file? My guess is that it a holdover from the early VLAN configuration process, and as long as I have a switch acting as a VTP server, I can discard the vlan.dat in the router's flash. Yes?
Is your router is having switch module? Was is also working as a VTP server?
If you already have a VTP server in your network up and running you can delete vlan.dat file and it will get updated on this router once you put it back into the network.