An embodiment includes issuing an indication that a thread is a time-critical thread. The embodiment initiates an active partition migration, from a source server to a destination server, of a source partition on which the program is stored. The embodiment stores, during the migration, records of locations of pages in memory referenced by the time-critical thread. The embodiment detects that a migration threshold has been reached, indicative of a threshold portion of the migration being complete. Responsive to detecting the migration threshold, the embodiment performs a priority migration of the time-critical thread. The priority migration includes suspending execution of the time-critical thread at the source server, retrieving the records of the locations of the pages in memory referenced by the time-critical thread, and issuing a command to transfer content from the pages to the destination server. The embodiment also includes issuing a migration command to complete the migration.