At switchover, the backup application (now the primary) resets all transient circuits if checkpointing of the transient state was implemented. If transient state was not maintained, the new primary application can either:
Reset all idle circuits.
Allow ISUP or TUP to recover transient circuits. This could take considerable time, depending upon what state the circuit was in at the time of switchover. Any attempt at using one of these circuits before the protocol has returned the circuit to idle state results in an error returned from ISUP or TUP.
Assume that the instance ID parameters (suInstld and spInstld) are set to 0 after a switchover.