1. A method for transaction processing in a massively parallel processing (MPP) database, the method comprising: receiving, by a transaction manager, from a first resource manager, a first snapshot of the first resource manager, wherein the first snapshot is a list of current active transactions on the first resource manager; receiving, by the transaction manager, from a second resource manager different from the first resource manager, a second snapshot of the second resource manager, wherein the second snapshot is a list of current active transactions on the second resource manager; reconciling the first snapshot of the first resource manager and the second snapshot of the second resource manager to generate a reconciled snapshot, wherein the reconciled snapshot comprises a union set of the first snapshot and the second snapshot, the first snapshot comprises a local transaction identifier (ID) for a first current active transaction on the first resource manager and the reconciled snapshot comprises a global transaction ID for the first current active transaction, and the global transaction ID is assigned by the transaction manager to the first current active transaction indicating the first current active transaction being performed remotely from the first resource manager; transmitting, by the transaction manager, the reconciled snapshot to the first resource manager and the second resource manager; and performing the first current active transaction using the reconciled snapshot.