Hi Ashwini,
SAP Provides with five different scenarios in RDS. It depends on which scenario you are going with.
There is a scenario which it integrates with ECC. If you want this scenarios to be activated then you need to first install the ERP 607 RDS and then PPM RDS. And also you have standlone scenario where we can use only PPM , this scenario does not require the ERP RDS.
If you have already tried to configure the system with best practice manually , i suggest to reset the config using cust copy transaction and run the RDS. But to run the rds you need couple of addon's to be installed.
Thanking
Vengaiah