Teradata Unity sends request-specific context information as part of a request that calls an external procedure to enable Vantage to change the result of the executed procedure indirectly by substituting a value predefined by Teradata Unity for a non-deterministic result. Vantage makes this context information available to an external procedure when it is called from the default connection for the session.
However, external procedures can generate and use their own arbitrary non-deterministic values that Vantage has no knowledge of. Therefore, Vantage cannot guarantee that an external procedure call produces a consistent result.
An external procedure can create a separate connection to another database, or to the same database by means of logging onto another session. In this case, the Teradata Unity-provided context information is not available for any SQL submitted using this type of connection.