See how using CNAMEs during SQL migrations can reduce risk and save time with fever reconfiguration needed.
Migrations are full of risk and CNAMEs offer a great way to mitigate some of that risk. It also saves a lot of time and reduces overall configuration complexity.
If you are brave enough to do in-place upgrades then this one isn't for you though.
For the rest of us however there is a simple way to point all the old server names to your brand new SQL installation, just use CNAMEs.
Imagine a SQL migration. After migrating all content off SQL servers marked for deprecation, you now need to go reconfigure all your applications and clients connecting to that old server.
It sounds painful, and luckily there is an easier way.
1. Simply rename the old server (let's call it OLDSQL1) to a new name(OLDSQL1_OLD works well)
2. Add a new CNAME record in DNS using the old server name that points to the SQL AG listener(SQLTARGET1).