We wish to user table partition on existing database table, we took export dump, renamed table and try to create new table with partition, but errora message is 'Partition feature is not enabled'.
If its Standard Edition then Partitioning Option is not available. In EE Partitioning option should be enabled by default.


Is there need to re-install the oracle in custom mode and enable partition feature?
You can do custom installation and choose partitioning option.


Is there any impact on existing database?
No it wont effect any DB

HTH