It' s possible use a sap abap in order to clean the bw infocube dimension. In attach of 1622324 note on the OSS there is a abap code.
The name of program is ZSAP_DIM_CLEANER
In order to show the actual dimension of all infocubes run the program SAP_INFOCUBE_DESIGNS
The deletion of entry in the dimension allow a better performance in write and read data of cube.