Access to and from Non-Oracle Databases
Oracle??™s Transparent Gateways (illustrated in Figure 13-1) are Oracle software products
that provide users with access to non-Oracle databases via Oracle SQL. Oracle
SQL is automatically translated into the SQL of the target database, allowing
applications developed for Oracle to be used against non-Oracle databases. You can
also use native SQL syntax for the target database, which can be sent directly to the
target without translation. Oracle datatypes such as NUMBER, CHAR, and DATE
Accessing Multiple Databases As a Single Entity | 307
are converted into the datatypes of the target. Oracle data dictionary views are
provided for target data store objects. As with Oracle databases, heterogeneous databases
can be linked to Oracle through database links to create a distributed database.
The gateways can be deployed in a two-tier architecture in the Oracle database or in
a middle tier (Oracle Application Server).
There are four basic types of database connectivity provided:
Open Database Connectivity
Generic ODBC and OLE DB interfaces are free and are bundled with the Oracle
database.
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