Before Release 8.0.1, when you change the primary, secondary, or both Session Managers, the existing call history was preserved. However, the new Session Manager moves the call logs from the old primary, secondary, or both Session Managers to the new primary, secondary, or both Session Managers. With Session Manager Release 8.0.1 or higher, the call history movement to new Session Managers is not required since all the call log data is stored on up to two Session Manager instances per Data Center.