cube to cube load is very slow

In any data warehouse, this is a frequently common requirement to push data from one cube to another.

My cube to cube load through DTP takes a long time in "Find or take SIDs" step.

Transformation is one-to-one mapping with NO modifications to data at all. We are NOT performing any master data read while loading the cube.

We turned ON Number Range Buffering in Main Memory with 500 buffers. NO luck.

Please suggest.