how to make two oracle server to be updated ?

hi
1 i have an oracle 7.3.4 on digital unix with 20gb database 2 i have build the same database on oracle 8.0.4 on NT. now i need a way to synchronise between the server but not in a real time (can be a script that run every 6 hours) so the two database will have the same data , and again ,it is not critical if there will be a delta of time when the two databases will no be equal .

ps i cant use replication

thank for advance

          zohar oshrat
          sys admin