These are quite...exclusive SAS storage formats, and are usually not created out of the blue.
If your organisation uses these formats you should go to the source of their orgin.
MDDB - PROC MDDB, legacy SAS V8 cubes.
DMDB - %em_dmdb, pretty sure Enterprise Miner is requred.
FDB - consolidatio DB, not sure here but is probably part of SAS fiancial portfolio. Can't find any open documentation that support this file type.
Data never sleeps