SYSVIEW's UPDATE mode is functioning as designed and expected. When using UPDATE mode through different interfaces, there are differences in the way command input is handled.
1. TSO will issue a command after the update time expires.
2. ISPF will ignore the command, the command cannot be entered until using ATTN to back out of UPDATE mode. If in a "split screen" session, the user is unable to switch to the other screen while UPDATE mode is active.
3. VTAM will process the issued command while continuing with the update interval.