by default a BGP session do not shutdown until the Hold timer times out. In Huawei Keep-alive is 60s and Hold-time is 180s. So if we are in multi ISP environment and internet peer go down, the networks preferred by the failed peer are black-holed.
With the command:
The BGP router clear the peer session immediately if the interface go down so IGP can recalculate a new path for lost networks.