Sybase <-- Oracle

We are running a 7.3.2.1.0 oracle dbms in a RS6000 with AIX, and some SYBASE DBMS in a windows NT 4.0, and want to connect from the NT to the RS6000 to share some information stored in one oracle database. I know that we need a gateway in the RS6000.
But, i wonder if we have to buy it, or if it comes with the dbms software?

and if comes with the dbms software, how i install it?

thanks.

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