When I worked on MVS/XA via VTAM in the 1990s, Attn could interrupt any TSO program doing terminal I/O using Attn. PA1 produced a similar response from TSO, with the vertical bar on screen, except that it could not be sent while the terminal was locked.
With Vista,? x3270 and wc3270, Attn gives me nothing, even at a READY to prompt. Yet if i press it a few times, I suddenly go to the VTAM logon screen. Meanwhile, PA1 will sometimes interrupt, and sometimes not.
