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About SDH Tables
The UCM Source Data History tables (SDH tables) contain the transactional contact and account data records pertaining to Siebel UCM and registered external systems. These tables hold incoming, best version, and historical data records, and provide the content for the UCM administration views. The storage of this data allows for Siebel UCM features such as survivorship, merge and unmerge, and so on.
The SDH tables are named with the S_UCM_* prefix such as S_UCM_CONTACT and S_UCM_ORG_EXT. The UCM base tables are the tables that are visible from the Siebel application such as S_PARTY, S_CONTACT, S_USER, and stores the master copy of the record.
The SDH tables ultimately contain a large amount of data and must be purged at regular intervals. For further information on this task, see Purging Source UCM Data.