Hi,
Install the DatabaseCleaner from the Forge.
DB Cleaner Forge
You can use this tool to clean up your database

You can also use the SQL Sandbox from Forge if you want to clean data from your entities with SQL outside Service Studio
SQL Sandbox

Kind regards

Thibaut 

I can assume , you would not be able to install new application to delete or clean the data. So you can delete the app that is now not required you , you can save it locally for future reference.

Also follow the below one 
https://success.outsystems.com/documentation/11/managing_outsystems_platform_and_application_lifecycle/best_practices_for_a_tidy_and_clean_environment/

hi @jensing sam ,you may need to clean your personal environment, as Outsystems provide only 2GB of storage for personal environments, you can delete unused apps, clean old data, purge logs. You can use the techniques proposed above to achieve your goal.

you can also request a Factory Reset via OutSystems Support. This willl clean your environment freeing all space but deleting all apps & data. 

Hi @jensing sam ,

First, check the ossys_espace table and verify its total size. Make sure you can access Service Center. If you can, manually delete older versions of your published modules until storage usage is reduced from 150% back within the 100% limit. After that, you can use the DB Cleaner and other tools to monitor details such as which modules are consuming more space and the overall database usage. 

As Amit said this article will guide you through it.
https://success.outsystems.com/documentation/11/managing_outsystems_platform_and_application_lifecycle/best_practices_for_a_tidy_and_clean_environment/