data-konzept

'When you perform online index operations, the following guidelines apply: 

• Clustered indexes must be created, rebuilt, or dropped offline when the underlying table contains the following large object (LOB) data types: image, ntext, and text. 

• Nonunique nonclustered indexes can be created online when the table contains LOB data types but none of these columns are used in the index definition as either key or nonkey (included) columns. 

• Indexes on local temp tables cannot be created, rebuilt, or dropped online. This restriction does not apply to indexes on global temp tables.

• Indexes can be resumed from where it stopped after an unexpected failure, database failover, or a PAUSE command. See Alter Index. This feature is in public preview for SQL Server 2017 and Azure SQL Database.'...

https://docs.microsoft.com/en-us/sql/relational-databases/indexes/guidelines-for-online-index-operations