The keys that talk to the host
A 3270 terminal does not send each keystroke. You fill in the screen locally, and only an attention key (Enter, a PF key, PA1, PA2 or Clear) sends it to the mainframe. All the other keys, such as Tab, Erase EOF and Reset, act only on your own screen.
Two kinds of keys
The technical name for these is attention identifier keys. When you press one, the terminal sends the changed fields plus a code saying which key you pressed. The application then decides what Enter, PF3 or PF8 means on that panel. That is why the same key can do slightly different things in different products.
The PF keys you will press all day
| Key | Usual meaning in ISPF and most products |
|---|---|
| PF1 | Help, or the long form of the current message |
| PF3 | End: save if relevant and go back one level |
| PF4 | Return: jump straight back to the starting menu |
| PF5 / PF6 | Repeat the last find / repeat the last change |
| PF7 / PF8 | Scroll up / down |
| PF10 / PF11 | Scroll left / right |
| PF12 | Usually Retrieve (recall your last command). On some panels it is Cancel |
| PF13–PF24 | Shifted PF1–PF12. By default most do the same as their partner |
PA1, PA2 and Clear
- PA1 is the attention interrupt. In TSO it stops a command that is running or listing too much.
- PA2 asks the application to redisplay the current screen. In ISPF it restores a panel you have scribbled on.
- Clear blanks the screen. In ISPF it is mostly harmless. In a CICS transaction it can end what you were doing, so use it on purpose.
When the keyboard locks
The bottom line of the emulator is the operator information area. When it shows an X with a symbol or the word SYSTEM, input is inhibited. If the host is busy, wait. If you typed somewhere you are not allowed, or into a full field, press Reset and try again.
4A MA a 03/015 ready 4A MA X SYSTEM host is working: wait 4A MA X -f you typed somewhere you may not: press Reset
Which PF key takes you back one level (End) in ISPF? Type it as PFn.
Show a hint
It is the key you press thousands of times a week.
Show the solution
PF3 is End. PF4 is Return, which goes all the way back.
Examples are for learning. Run commands and jobs only on a system you are authorised to use, such as a training or test system, and never on production without approval.
Common mistakes
Enter sends the whole screen to the host. Use Tab or the New Line key to move down to the next field.
Everything typed while X is showing is discarded. Press Reset once, then retype.
Many CICS programs treat Clear as 'end this conversation'. You can lose what you entered.
What you will see at work
- Support runbooks are written in key names ('press PF8 to the bottom, then PF5'). Learn the names, not just where they sit on your keyboard.
- PA1 is how you stop a TSO command that is printing thousands of lines.
- If a colleague's PF keys behave differently, they have probably customised them with the KEYS command.
Key terms
Check your understanding.
Take this lesson's quiz and save your progress. Free.