What is an In-Place upgrade in SQL Server?
In SQL Server, in-place upgrade is the way to upgrade existing SQL instances to a higher version or edition without changing the server name and hardware.
We can perform this activity without moving the database, logins, jobs, and other objects to the new server.
During the SQL Server in-place upgrade, the SQL server installer copies all required binaries of the new version/edition on the existing instance or setup, upgrades required binaries, and necessary system files on the server. This activity also updates system databases as well as such as all user databases.
The best part of SQL Server in-place upgrade is that it requires less downtime than side-by-side.
It is also cost-effective because no need to buy new hardware or licenses.
But before implementing on the production server, implement on the test/dev environment & test properly. Check whether the application os compatible with a higher version/edition or not.