Note:
Many of the rules for heterogeneous access also apply to remote references. For more information, see the distributed database section of Oracle Database Administrator's Guide.
A SQL statement can, with restrictions, be executed on any database node referenced in the SQL statement or the local node. If all objects referenced are resolved to a single, referenced node, Oracle attempts to execute a query at that node. You can force execution at a referenced node by using the /*+ REMOTE_MAPPED */ or /*+ DRIVING_SITE */ hints. If a statement is forwarded to a node other than the node from where the statement was issued, the statement is remote-mapped.
There is complete data type checking support for remote-mapped statements. The result provides consistent data type checking and complete data type coercion.
SQL statements must follow specific rules to be remote-mapped. If these rules are not followed, an error occurs. The order in which the rules are applied does not matter. See Important Restrictions for these rules or restrictions.
Different constraints exist when you use SQL for remote mapping in a distributed environment. This distributed environment can include remote Oracle databases and non-Oracle databases that are accessed through Oracle Database gateways.