I don't think there are any IOS commands to 'view' the vlan.dat file, however it is pretty easy to copy it onto a TFTP or FTP server and view it from a PC. It isn't really readable though (I have just tried it with a switch I use at home).
If you just want to view the VLANs on the switch, just use 'show vlan'. This will show you what VLANs are configured on the switch and which ports are in which VLAN.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...