-- here i have used the convention of having
-- db link name same as service name ( tnsentry)
[b]create database link mylink[/b] --[i]this is db link name[/i]
[b]connect to userA identified by somepassword
using 'mylink';[/b]--[i]this is service_name[/i]
-- i will use the above link like
[b]select * from tablename@mylink;[/b]