In case of multiple lines of productions environment every cell + portal cluster will have its own release database but they will share customization database, because of this if user customizes any of the resource using one cluster those changes would be available when same user will access the resource even through other cluster.
Since multiple lines of production will share the customization database they should be exact replica of each other, i.e. the object ids of the resource such as portlet or page should be same in both lines of production. In order to make sure that object ids are same you will have follow some additional guidelines in case of multiple lines of production
First you will need to execute empty-portal configuration task on both lines of productions to clean it up during the setup process. Once that is done you will have to export configuration from the staging environment and import same configuration with ID generation mode set to false. this will make sure that the portal does not generate object ids while importing portal configuration.
You should use the release builder tool to build subsequent releases