Terminal LU state requirements

When Debug Tool accesses the terminal LU, the terminal LU must be in the following state:

It must be known to the z/OS® Communications Server on the system which Debug Tool runs.
It must be marked secondary logical unit (SLU) enabled.
It must not be in session with any application.

You can determine whether a particular terminal LU meets these criteria by using the DISPLAY VTAM® operator command:

Access the desired LU using your terminal emulator, and exit any session manager.
On your system console, enter the following command, where name is the LU name:
```
DISPLAY NET,ID=name,SCOPE=ALL
```
Inspect the output of the command for the following information:
- The IST486I message indicates STATUS=ACTIV and DESIRED STATE=ACTIV, and an IST172I NO SESSIONS EXIST message is displayed.
- The IST597I message indicates SLU ENABLED.
- The IST934I message indicates that a DLOGMOD was specified.