Gateways
Oracle has responded to the need for access to non-Oracle databases such as IBM’s DB2 by developing gateway products. These gateways run as processes on the non-Oracle host machine, and essentially operate by emulating SQL*Net and an Oracle database on the non-Oracle host. For example, IBM provides a native SQL database on its AS/400 computers, which are very popular small office machines. Oracle does not have a database product that runs on AS/400, but it does provide an AS/400 gateway. This gateway has a listener process that functions just like the listener on any Oracle server, and is used to establish connections to Oracle servers. Once a connection is established, gateway software translates Oracle SQL queries into native AS/400 queries, and then returns the data to the Oracle server, essentially making the data stream look as if it had come from another Oracle server.
One restriction on the use of an Oracle gateway is that it can only be accessed from an Oracle server using a database link; an Oracle client is not able to directly connect to a gateway.
Tip
Not all gateways support Oracle’s two-phase commit mechanism for distributed transactions. If you require this functionality, consult the appropriate Oracle documentation for the gateway.
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