How Repository Identifiers are Stored and Instantiated
A site identifier (site ID) is a portion of the internal identifier (or internal object-version identifier) of a repository object. A globally unique identifier (GUID) is a portion of an object identifier (or object-version identifier).
There is a one-to-one correspondence between a site ID and its GUID, and each repository database includes a table (RTblSites) that maintains this correspondence. Each row of the table associates one GUID with one site ID.
The repository engine uses the one-to-one correspondence between the site identifiers and GUIDs to conserve space in the repository database. When the repository engine stores a repository object, it stores the internal identifier with the object. The engine does not store the GUID or the object identifier with the repository object. When you need to retrieve the object identifier of an object, the repository engine constructs the object identifier by reading the internal identifier stored with the object, matching the site identifier to the appropriate row of the RTblSites table, and reading the GUID from that row.
See Also
Object Identifiers and Internal Identifiers
Object-Version Identifiers and Internal Object-Version Identifiers