Hello Padhmanaban P,

For database migration best way  is open upgrade, in that you can take clone from https://github.com/OCA/OpenUpgrade and checkout in respective branch.

you can go through V11 to V12 , then v12 to v13 and V13 to V14.

https://doc.therp.nl/openupgrade/intro.html#migrating-your-database

In that first clone openupgrade with branch 12 and put your DB which is in V11 and resolved issues facing in terminal and after that Your DB is migrated in V12 .first check data is in v12 is proper or not then after you will start V12 to V13 respectively.

Hi,

You can refer to the blog "How to Migrate Odoo Database Using OpenUpgrade" on the Cybrosys blog for detailed step-by-step instructions on how to migrate a database from Odoo 11 to Odoo 14 using OpenUpgrade. The blog should provide you with comprehensive guidance on how to perform the migration process, including preparing the data, installing Odoo 14, creating a new database, installing required modules, using OpenUpgrade to transfer data, testing and validating the migrated data, and updating customizations. Following the instructions in the blog carefully should help you successfully migrate your Odoo database from version 11 to version 14.

Refer this Link:

https://www.cybrosys.com/blog/how-to-migrate-odoo-database-using-openupgrade

Regards