3GPP 24.501 v20.0.0 — the document's own text
5.1.3.2.2 5GS update status in the UE
Taught in 5. Finding your way around TS 24.501 (CT1 — the group that writes what your phone says, in depth), 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).
In order to describe the detailed UE behaviour, the 5GS update (5U) status pertaining to a specific subscriber is defined.
If the UE is not operating in SNPN access operation mode (see 3GPP TS 23.501 [8]), the 5GS update status is stored in a non-volatile memory in the USIM if the corresponding file is present in the USIM, else in the non-volatile memory in the ME, as described in annex C.
If the UE is operating in SNPN access operation mode, the 5GS update status for each SNPN whose SNPN identity is included in the "list of subscriber data" configured in the ME (see 3GPP TS 23.122 [5]) is stored in the non-volatile memory in the ME as described in annex C.
The 5GS update status value is changed only after the execution of a registration, network-initiated de-registration, primary authentication and key agreement, service request, paging procedure, due to a 5G-GUTI deletion in state 5GMM-REGISTERED (see clause 5.3.15A) or due to change in the current TAI which does not belong to the current registration area while T3346 is running.
5U1: UPDATED
The last registration attempt was successful.
5U2: NOT UPDATED
The last registration, network-initiated de-registration, or service request attempt failed procedurally, e.g. no response or reject message was received from the AMF.
5U3: ROAMING NOT ALLOWED
The last registration, service request, primary authentication and key agreement, or network-initiated de-registration attempt was correctly performed, but the answer from the AMF was negative (because of roaming or subscription restrictions).