Mixing : Automation : Automation Modes : Trim Mode

Trim Mode
(Pro Tools HD and Pro Tools with Complete Production Toolkit Only)
Pro Tools HD can adjust (or trim) existing track volume and send level automation data in real time. Pan, mute and plug-in automation cannot be trimmed in this manner. Trim mode works in combination with the other Automation modes (Read, Touch, Latch, Touch/Latch, and Write) and is useful when you want to preserve all of your volume automation moves, but need to make levels a bit louder or softer to balance a mix. For more information, see Trim Automation Modes.
When writing automation in Trim mode, fader moves write relative rather than absolute values. The existing automation data is changed by the amount of increase or decrease (or the delta value) indicated by the faders.
When Trim mode is enabled, non-trimmable controls behave in the same manner as in the standard Automation modes, with the exception of Write/Trim mode, where non-trimmable controls operate as in Touch mode.