Release Notes.

IMPORTANT INFO regarding SP6 HF00 (full installation)
Extension Indexes transport RTCK900222 should be done outside business hours for productive S/4 HANA systems, as it can trigger recompiling of all development objects.

IMPORTANT INFO regarding SP5 HF00 (full installation)
Extension Indexes transport RTCK900143 should be done outside business hours for productive S/4 HANA systems, as it can trigger recompiling of all development objects.