I recently had to pull the official documentation on this myself. Please refer to the SRND for the version in question beginning at 8.0. No such thing as ADS... maybe you meant AW-HDS
Again, you'll need to look at the SRND for specifics. It is clearly documented there. Let me know if you need help finding that document.
The Historical Data Server (HDS) and Detail Data Server (DDS) are used for longer-term historical data storage. The HDS stores historical data summarized in 15 or 30 minute intervals and is used for reporting. DDS stores detailed information about each call or call segment and is used for call tracing. Data may be extracted from either of these sources for warehousing and custom reporting.