Do you know which database(s) you have available on your Linux system? In general, the process is the same: find the appropriate database driver, add it to your classpath, and then connect to the database using JDBC. I've moved this to the JDBC forum, where it will get more appropriate attention.
I have my Oracle 8i database in another Linux machine, so how do i access it from my Linux machine. What are the configurations needed to be done. And for the same what has to be done if the Oracle is on a windows machine.
The configuration should be the same except for the machine name in the jdbc URL. There have been lots of examples in this forum. A search for "oracle" should bring up plenty