Maybe, I was not using the right words to search, but I looked for the answer in this group and googling but failed to find the response to my question:" how do you migrate from an existing sqlite database to freshly installed postgresql database ?"
In order to migrate from SQLite to PostgreSQL, you’ll have to do full replication from the old Orthanc running SQLite to the Orthanc running PostgreSQL. Replication is explained in the Orthanc Book:
Thank you for your quick response. I’ll dig into that.