By default,in Virtual DataPort the option to write into source tables is enabled when you connect to RDBMS sources like Oracle or SQL Server using JDBC data source.
Moreover, you can check if the data source can perform inserts and updates by following these steps:
1. Open the base view.
2. Click on "Options" tab and press on "Search methods" tab.
3. Click on "wrapper source configuration" link. Here you can check if you have the "Allow insert" and "Allow update" configuration set to "Yes".
I hope this helps you!