Example of requirement when it's reasonable to use *WHEN_REF_DATA=MASTER_DATA
On the DM prompt user entered some value to be stored in the cube, but at that moment there is no data in the intersection where the value to be stored:
*XDIM_MEMBERSET SOMEDIM=SOMEMEMBER
*WHEN_REF_DATA=MASTER_DATA
*WHEN SOMEDIM
*IS *
*REC(EXPRESSION=$USERVALUE$) //$USERVALUE$ - entered by user.
*ENDWHEN
Unfortunately *WHEN_REF_DATA=MASTER_DATA affects ALL dimensions, you have to define narrowest possible scope (and even with narrow scope it can be slow).
Please, provide the full script!
Vadim