Hi Amit ,
Did you happen to check the following notes
2080618 - SUIM | Performance of change log reports RSUSR100N, RSSCD100_PFCG, RSSCD100_PFCG_USER
1648187 - SUIM|Performance in report RSUSR100N
Did you try ST12 tracing and try to find where the actual issue is ie DB level / application level
Thanks ,
Manu