Step 1
Why you need to upgrade
https://pro.arcgis.com/en/pro-app/3.0/help/data/geodatabases/overview/client-geodatabase-compatibility.htm#:~:text=10.8.1.2.6,10.8.1
Step 2
How to check your current geodatabase version
Step 3
you must be system admin role in SQL server to be able to upgrade
Step 4
geodatabase upgrade finished
Step 5
one SQL server have so many database, you will have to manually upgrade each one by one.
Step 6
another way to upgrade geodatabase, it is same as previous
Step 7
You must disconnect all user connection and all user lock before upgrade, otherwise, you will see this error