I require help from database stalwarts for the issue mentioned below.

We have two database oracle and db2, MAINFRAME installed on two different systems.Online applications updates/inserts data in DB2 and updates/inserts some information in Oracle database also. But there are some native implementation, which updates data in the db2 dATABASE but they do not update any data onto the oracle database.

Now the need is we need this two database to be in sync. How do we acheive it?
If we set triggers that would be applicable for any modification/insertion on the tables in DB2 but this would also lead similar action for web based online application. The synchronisation is not required for online applications since it updates both database tables. Second constraint we cannot modify the legac/ native applications which insert data in the db2 database only.

thanks for help