If you require a Cisco device to act as a DHCP server. Do ensure you either set a database URL or the no ip dhcp conflict logging option otherwise the server can fail leaving your users free to complain that “the internet is broken”. I prefer to use a database agent.
Now you can either use local flash or a tftp/ftp server or of course both. You just need a config line using the following url format:
ip dhcp database tftp://<tftp server address>/DHCP_Binding/dhcp_db ip dhcp database flash0:/DHCP_Binding/dhcp_db
Of course you need to check which flash you have on your router and make the location first using standard UNIX commands.
You need to do whats required on the TFTP server side also and test if you are using a separate server as a logging destination. Once these are implemented then you can check if the file exists. It is just a plain text file. You can also check the status of the dhcp server using:
sh ip dhcp database
Some other useful docs: