Index need to be check when migration the database server

We migrate our Oracle Database one server to another one.
we cross checked the two databases . all were OK.
even if parameters, memory size, objects , network all were ok

but our new database was performing very slow for some application reports,
programs...
we can't able to find. whats the cause??

after three days, we find that two big index were not import to new server.
after creating these. we solve our problem.