Re: effect of dc change on running database server
resolv.conf is for DNS only.
DC shutdown may bring us catastrophic effects. It actually depends on your env. But, you already activate the new DC and now you are concerned about the active/old connections.
The ability to reconnect an Oracle Database depends on the application side actually.
What do you use in the application side?
What do you use for connecting to the Oracle Database in the application side?