About Bind Variable

http://umardba.blogspot.com/2009/11/bind-variables-key-to-application.html

Bind variable peeking:

http://www.dbspecialists.com/specialists/specialist2003-11.html

Statistics gathering..

http://download.oracle.com/docs/cd/B10500_01/server.920/a96533/stats.htm

Objects are considered stale when 10% of the total rows have been changed. When you issue GATHER_TABLE_STATS with GATHER STALE, the procedure checks the USER_TAB_MODIFICATIONS view. If a monitored table has been modified more than 10%, then statistics are gathered again. The information about changes of tables, as shown in the USER_TAB_MODIFICATIONS view, can be flushed from the SGA into the data dictionary with the DBMS_STATS.FLUSH_DATABASE_MONITORING_INFO procedure.