If Start is clicked for a Reconfiguration Plan with Operational Status of Preparing, a confirmation dialog box appears advising to resolve resource user and resource provider problems prior to starting the migration. The user can choose to cancel the starting of the migration and resolve problems, or choose to continue and start the migration anyway. If Start is clicked for a Reconfiguration Plan with Operational Status of Prepared, the Administrative State is set to Start, the Operational Status is set to Migration Started, and the migration of SBR data begins.
After starting a Reconfiguration Plan the Operational Status changes to Migration Started for a short period before transitioning to Migration Coordinated. The reason for the Migration Started status is to solve race conditions that could occur as all resource users begin executing data migration logic. When Start is clicked, the NOAM replicates a command down to all resource users to begin data migration. Since this command cannot reach every resource user at the exact same instant, some resource users may begin migration before others are aware that migration is starting. This difference can result in split bindings in which one session for a subscriber and APN is routed to one PCRF and another session for the same subscriber and APN is routed to a different PCRF. To avoid this race condition, the resource users are put into a special mode where they create records in both the initial and target resources. This mode lasts until all resource users report that they have started migration, or until a timer expires in less than a minute and the NOAM commands them to go to the Migration Coordinated mode.
Once in the Migration Coordinated mode, the resource users create all new records in the Target Resource Domain or Target SBR Database and look for all records there first. If a record is not found in the Target, another query is launched to the Initial Resource Domain or Initial SBR Database. The Migration Coordinated mode continues until the data migration is completed.