
A dimension/hierarchy can only appear once in the whole layout. For example, in a page axis, you cannot place two members of the same dimension/hierarchy in different cells. The following is an invalid report since it is impossible to determine if the whole report should contain data for Canada or for the USA:

Similarly, a dimension/hierarchy in the row axis cannot have a member appear in the page axis or in the column axis or vice-versa.
The following reports are also invalid since there is no data that represents both January and April at the same time:

The Period dimension appears both in the row and the column axis.

The Period dimension (Apr) appears in the page axis and in the column axis.