All the systems mentioned in this section (IGD, Docking-D, Entrez, SRS, LinkDB) need to synchronize their content with their component MBDs. These synchronizations are not trivial and therefore frequent (e.g., daily) synchronizations are seldom supported.
The data synchronization in IGD is done incrementally when incremental updates are supported by component MBDs. SRS and LinkDB do not support incremental updating - the index files must be rebuilt for every update.
IGD, Docking-D, SRS, and LinkDB currently involve over 10 component MBDs. Entrez is more specialized and therefore involves fewer MBDs. Incorporating new MBDs into these systems requires resolving schema and data conversion issues.