Yes, it is possible to upgrade from Odoo 9 to Odoo 15 using OpenUpgrade. OpenUpgrade is a community-driven project that provides a set of tools to upgrade Odoo databases from one version to another.

To start the upgrade process, you will need to follow these steps:

1. Backup your Odoo 9 database: Before starting the upgrade process, it is important to create a backup of your Odoo 9 database to avoid data loss.

2. Install OpenUpgrade: You will need to install OpenUpgrade on your Odoo 9 server. You can download the latest version of OpenUpgrade from the official repository on GitHub.

3. Configure OpenUpgrade: Once you have installed OpenUpgrade, you will need to configure it to connect to your Odoo 9 database. You can do this by modifying the openerp.cfg file in the OpenUpgrade directory.

4. Run OpenUpgrade: Once you have configured OpenUpgrade, you can run the upgrade process by executing the run.py script in the OpenUpgrade directory. This will analyze your Odoo 9 database and perform the necessary changes to upgrade it to Odoo 15.

5. Verify the upgrade: After the upgrade process is complete, you will need to verify that everything is working correctly in Odoo 15. You can do this by testing the functionality of your Odoo 15 installation and checking that all of your data has been migrated correctly.

Note that the upgrade process can be complex and time-consuming, and it is important to have a good understanding of Odoo and database management before attempting an upgrade. It is also recommended to perform the upgrade on a test environment first before upgrading your production environment.

Hi,

If You are using Odoo Community Edition You can use Open Upgrade scripts

https://www.cybrosys.com/blog/how-to-upgrade-the-odoo-15-database-using-openupgrade

Here are the scripts https://github.com/OCA/OpenUpgrade/tree/9.0

Regards