VIT control levels

VTAM® provides two levels of operator control for managing the VIT in internal mode. You can select what level of control is appropriate for your environment. The level of controls primarily affect certain default VIT options (API, CIO, MSG, NRM, PIU, and SSCP). This set of options represent the minimum required options for diagnosing VTAM problems. You can choose one of following two levels of control:

Base Control
You can choose to allow VTAM to enforce that certain default VIT options remain active at all times. This is the default setting. With this level of control, you cannot use the MODIFY NOTRACE command or the NOTRACE start option to disable these VIT options. If you attempt to disable these VIT options, VTAM accepts the command or start option but immediately re-enables the VIT options.

When using this "base" level of control, VTAM does not always display the setting of these default VIT options as output to the DISPLAY TRACE, MODIFY TRACE and MODIFY NOTRACE commands. The settings are not considered user controllable and are therefore only displayed if you have explicitly enabled the VIT option by using the TRACE start option or the MODIFY TRACE command. If you later explicitly disable the VIT option by using the MODIFY NOTRACE command, the VIT option is no longer displayed but remains enabled.
Full Control
You can choose the ability to disable individual VIT options at any time by using the MODIFY NOTRACE command or the NOTRACE start option.

When using this full level of control, VTAM always displays the current setting of these default VIT options as output to the DISPLAY TRACE, MODIFY TRACE and MODIFY NOTRACE commands.

If you use the VIT in external mode, you always can disable all VIT options.

Result: Disabling any of the default VIT options for internal VIT processing can trigger a health check notification (CSVTAM_VIT_OPT_STDOPTS) and impacts VTAM serviceability.