I have read a lot of topics on the issue of missing data in OLAP cubes and found that the reason can one of the two below

1) NULLS in fact table

2) Missing values in dimensin table

For 1) the soultion is to update NULLS with NA/bad (or similiar) and include this in all dimension tables.

But what about 2). How can this be taken care of so that records are not missing in the cube?