GlobalDB (GDB) is the distributed data storage with atomic changes that can be syncronized over the network. In other words, it is an aggregate of databases (installed and functioning on different network nodes), synchronizing common data with each other, according to a certain protocol - and thus constituting one large distributed ("global") database.
GDB is the basic subsystem of the Cellframe network. Each node in the network uses it to synchronize data shared with other nodes.
One of the synchronized key-value groups of the GDB is the so-called "whitelist" - a list of IP addresses of all nodes that make up the network. Whitelist is required in order for the nodes present in the network to know about the newly joined.
A special section of the GDB, called mempool, serves for temporary placement of consensus (and not only) chains data that appear in the network, until they are approved by the consensus algorithm (or, in the No-consensus mode, by a specially designated node) - and placed in a stable, unchangeable subsequently chain.
In No-consensus mode, the data chain itself is also stored in the GDB.
Any node can work, in principle, with any database, but for user nodes, built-in types of database drivers are preferable (CDB, SQLite and in the future, probably MDBX), and for server ones, more fault-tolerant (since it works in a separate process) PostgreSQL is preferable ... By default, CDB is used for user nodes.