Lesson Learned #330: Blocking issues Sch-M and Sch-S
Today, I worked in a very interested case. Our customer is trying to run an ALTER TABLE <TableName> to add two columns but this process is taking too much time, even, when the documentation reported "Starting with SQL Server 2012 (11.x) Enterprise Edition, adding a NOT NULL column with a default value is an online operation when the default value is a runtime constant. This means that the operation is completed almost instantaneously despite the number of rows in the table, because the existing rows in the table aren't updated during the operation" https://learn.microsoft.com/en-us/sql/t-sql/statements/alter-table-transact-sql?view=azuresqldb-current#adding-not-null-columns-as-an-online-operation
