Thanks for advise.
I have checked the db session wait for database link. Do you think the queries in the script below will force a full table scan causing waiting time to increase?
where substr(cdrfilename, 1,11) between '3gs00698947' and '3gs00700180'
where substr(cdrfilename, 1,15) between '3g3glf_00124907' and '3g3glf_00125968'
dbsessionWait.PNG