Implementing oracle Streams

Hi Everyone,

i need to implement streams from four sources to one target database.
These four sources have same type of schema but in table level columns are different.
At the target database i need to replicate 100 tables nearly through these four source database.
The requirement is i need to select some column's from those tables.

Please give me some idea or if you have any documents please send me.Like table level replication.


Please help me out with this situation
would be greatfull

Thanks
Ram