You can query the DBC.TableSizeV view to determine if data for a given table is evenly distributed across all AMP vprocs.
SELECT vproc,CurrentPerm FROM DBC.TableSizeV WHERE Databasename = 'RST' AND Tablename = 'Message' ORDER BY 2 desc;
The output lists the AMPs in order of the space they use for the Message table, from the most to least space used. See Example of Finding Skewed Tables by Querying the TableSizeV View.