The objects to be replicated must be in sync before you initiate the replication. If the data is not in sync before replication starts, there is a strong possibility that data conflicts can occur. For instance if a record is updated or deleted on the source database that does not exist on the target database. For one-way replication you can choose from following options depending upon the volume of data to be loaded into the target.

Oracle Data Pump
Standby Database
Rman Duplicate
Rman Restore and Recover
Transportable Tablespace ( Enterprise Edition Only)
LOAD function of Dbvisit Replicate

Datapump script is used when you have few tables/schemas to be replicated and the data volume is low.
Any of the option from 2, 3 and 4 can be used when you have many schemas to be replicated and the data volume is huge.
Transportable Tablespace is a wise choice over datapump for heterogeneous environment with the high data volume if you are using Enterprise Edition.

Browser not supported