Global DML commands behave as if they were executed on the coordinator, and obey the same locking rules as on a single server.
For example, if one transaction on any server has modified a shared IQ table, no other transaction may modify that table until the original transaction commits or rolls back. Whenever a global transaction commits, whether it runs on a writer node or the coordinator, the metadata for that global transaction is communicated to all servers in the multiplex through the TLV log.