Queries that start after a node has prepared cannot access the associated locked data until all phases complete.
A distributed transaction is ANY operation across a database link. It will result in a total table lock and access will be serialized. :(
This means a long running query for a data warehouse will lock the source tables for the duration of the transaction, until the client COMMIT's. It also means that the client will wait until it can obtain a table-level lock on the object. This behaviour is influenced by the system parameter DISTRIBUTED_LOCK_TIMEOUT.
It also implies that, SCN's are local, and foreign context is limited.
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