I would like to know what is the difference between high cardinality and line item?
Should I use high cardinality if number of rows in infoobject 11 mln but the number of rows in cube 41 mln records?
There is a relationship between High Cardinality and Line Item, but the settings are somewhat different.
Line Item dimension - does NOT create a dimension table. The SID for the InfoObject is actually placed in the cube, and a B-tree index built on that column. So there is one less table in the query.
High Cardinality - A dimension table is created, but the HC setting impacts (depending on the DB) the type of index that is built. With Oracle, normally bitmap indices would be built on the dimension columns of the fact table. However, with HC marked, a B-tree index is created.
If you can model the dimension so that only the one Characteristic in question is in the diemsnion, then mark it as a Line Item dimension. If you need to have more than the one Characteristic in the dimension , then I would probably consider marking the dimension as High Cardinality.