title: Query Slow After Oracle client updrade from 10g to 11g
body: <p>My team is migrating an application from a win2008 server with the Oracle 10g client to a win2012 server with the Oracle 11g client. Both servers are pointed to the same Oracle 12c database. The performance is very much slower on the new drivers, from nearly instantaneous to 1.5minutes on some queries. The query isn't complex either, it's a select all on a table filtered by date range and foreign key. The table is massive, it has around a million records inserted per day. This table has a composite primary key consisting of an index and the date, created in that order.</p>
  
  <p>How to find the history of queries ran? The older server has queries that are disappearing from v$sql too fast to catch. How could a change of the client impact performance so much?</p>
  
  <p>Update: Oracle is using a different index scan: index range on the 10g client and full index scan on the 11g client. I've tried the index_rs_asc hint, but it's only forcing a index skip scan. </p>