i need to migrate bamboo from embedded H2 database to External database without doing the custom installation again like migrate option in bitbucket
Bamboo does not have a migration feature like Bitbucket to perform such change. To migrate the DB in Bamboo you will need to export the database and import it in a clean installation with the selected DB. The process is described in this document:
We also have a feature request to provide Bamboo with the same process of DB migration that you see in Bitbucket:
Let me know if you still have questions on this matter.