The main differences between shared-nothing parallel databases and distributed
databases are that distributed databases are typically geographically
separated, are separately administered, and have a slower interconnection. Another
major difference is that, in a distributed database system, we differentiate
between local and global transactions. A local transaction is one that accesses
data only from sites where the transaction was initiated. A global transaction, on
the other hand, is one that either accesses data in a site different from the one at
which the transaction was initiated, or accesses data in several different sites