How is MN-initiated SN-Modification/SN-Change triggered in NSA?

Hi Experts,

How does SgNB Modification/Change start? In 3GPP & O-RAN specs and vendor documents, it is mostly mentioned about the produre- starting with SgNB Addition (change scenario) or Modification Request messages-, but not the triggering case. As much as I know, it might start with SCG failure. But what are the other scenarios that might trigger MN-initiated SN-Modification/Change in NSA? Can it also be triggered measurement-based? If so, which node (MeNB/SgNB) prepares the measConfig, and which measurement event can trigger it in MeNB?

When MeNB determines to start a handover, it may trigger a MN-initiated SgNB Modification/Change.

The case I asked is different from Inter-MeNB Handover with SN-Change (If that is the one you mention). In 3GPP (37340) and O-RAN specs, they are explained under different topics. It is for the case in which there is handover in SgNB (intra-/inter-gNB) side, but not in MeNB side. What triggers this case at MeNB, and how does MeNB decide to start the procedure (in case there is no handover in MN side)?

SN triggered SgNB Modification/Change is SN-initiated. MN-initiated cases are triggered at MN side.