Db2extev (external event handler thread) : The same as SIGUSR2.
db 2 extev(外部事件处理程序线程)：与SIGUSR2相同。
2
Externalthread: Threads on an external surface.
外螺纹在外表面上形成的螺纹。
3
According to connection method classification (1) threaded connection valves: valve with internal thread or externalthread, and pipe thread connection.