Restrictions and limitations

The exit must not change the:
- Address of any parameter in the address list
- Address of any parameter (in the two-word descriptor) other than the JCL parameter
- Maximum length of any parameter (in the two-word descriptor) other than the JCL parameter
If the exit changes any of the fields, the logon processor issues an error message to the console and an error message to the terminal, and then ends processing. For information about the address list and the two-word descriptor, see Entry specifications.
The exit must not activate the prompt mode HELP function or the exit will ABEND with a 0B0 system completion code.
TSO/E terminal users can change the characteristics of their user profile using the PROFILE command. Using PROFILE, users can define how they want to use the terminal. For information about the PROFILE command, see .
Any profile changes that a user makes are stored in the user profile table (UPT). The new characteristics then remain valid from one session to another. However, profile changes are not saved if you use a logon pre-prompt exit and the exit does one of the following:
- Supplies the UPT in the UPT parameter and sets the UPT bit on, or
- Sets the No UADS bit on
In either case, when a user logs off, the UPT is not updated with any PROFILE changes.