online Oracle database migration to different Oracle database release We currently have the following environment 

Source data center: 
1) OS: Oracle Enterprise Linux 5.7 
2) DB: Oracle Database Enterprise Edition 10.2.0.1.0 
3) Server Type: Physical Server 
4) Data Size: 450 GB(used)/ 2 TB (allocated)

Target data center: 
1) OS: RHEL 6.8 
2) DB: Oracle Database Enterprise Edition 10.2.0.4.0 
3) Server Type: Virtual on top of VMWare 

WAN connection between Source and Target Data Center is 10 Gbps

At the moment there are no Tape library on Target Data Center

We want to copy the database to Target Data Center without stopping production application on Source Data Center (online copy). 

Once database has been copied to target Data Center, we will do functional testing on target Data Center. 

After the result from functional testing is confirmed okay then we will do cut over to Target Data Center with maximum 4 hours downtime allowed.

We have tried the following methods: 
1) impdp - network link: failed, since the production need to be stopped 
2) RMAN duplicate database: failed, since source db and target db is in different release

Tried to install same Oracle release on target Data Center but the prerequisites from oracle said that we should downgrade the OS first to RHEL 5.7 (latest supported OS to run Oracle 11.2.0.1) and then upgrade to RHEL 6.8 after data migration. 

After checking with Red Hat, it is also not possible to downgrade to RHEL 5.7 and upgrade later to RHEL 6.8 as Red Hat said that it is major upgrade and should be performed with fresh install then migrate the OS settings.

Need advise on what is the best possible solution for this situation? FYI, Oracle Golden Gate solutions is out of question since we currently do not have allocated budget to purchase additional tools.

Thank you and best regards,

Amir
1) impdp with network link doest not need the production database to be stopped. This is the slowest method, as this needs to build everything from scratch, I am not sure this would finish in 4 hours.

2) RMAN duplicate fails between different versions because it tries to automatically open the database, and that will fail. But you can manually restore the database on the new host from the RMAN backups, then open it with alter database open resetlogs upgrade; and run the upgrade scripts immediately. With this method, you need downtime only to upgrade the database on the new host, should not take more than 30-60 minutes.

3) Streams does not require any license. You can just simply replicate the database, and start using the new database whenever you want to. This requires the least downtime, but the configuration and administration is cumbersome compared to other methods.