If there is not enough space

If you do not have enough space to copy the table and recreate all the indexes, determine whether dropping the nonclustered indexes on the table leaves enough room to create a copy of the table. Without any nonclustered indexes, the copy operation requires space just for the table and the clustered index.

Do not drop the clustered index, since it is used to order the copied rows, and attempting to recreate it later may require space to make a copy of the table. Recreate the nonclustered indexes when the command completes.