2PC is an acronym for 2 Phase Commit. This is a protocol by
which data being committed to a database is committed in two
phases. In the first phase, the transaction processor checks that
all parts of the transaction can be committed. In the second phase,
all parts of the transaction are committed. If any part of the
transaction indicates in the first phase that it cannot be
committed, the second phase does not occur. ODBC does not support
Transactions in SQL databases are expected to have "ACID"
features: Atomicity, Consistency, Isolation, Durability. A
two-phase commit (2PC) protocol is needed for guaranteeing ACID
properties of transactions which involve changing data in more than
one database. This can be the case in a transaction involving
tables attached from other databases or explicit access to remote
databases with rexecute().
The 2PC protocol needs to have a third party Distributed
Transaction Coordinator (DTC). Virtuoso supports Microsoft
Transaction Server (or MS DTC).
There are two ways of using MTS-driven distributed transactions
in Virtuoso. Virtuoso either initiates the transaction, or it
responds to a transaction.