I've not used it myself, but it was my understanding that Oracle did this. Phil Greenspun, in the mid-1990's [1]:

> "In Oracle, readers never wait for writers or vice versa. I can serve my 18,000 daily users. I can EXPORT a consistent backup dump. I can update a 20,000 row table. I can rebuild an index. All simultaneously."

[1]: http://philip.greenspun.com/wtr/oracle-tips.html

> but not as cleanly as this.

SQL Server looks pretty clean to me.

    ALTER INDEX IX_name ON schema.table REBUILD WITH (ONLINE=ON);