pool error timeout waiting for idle object

[sasidhar prabhakar]

My application sometimes responding very slow.
When I observed the logs, it is showing these lines

Cannot get a connection, pool error Timeout waiting for idle object.

The maximum connections on oracle I set 150.
When I query for present sessions or process it is showing 70 to 80 and
decreasing to minimum of
52, sometimes it grows up to 100 above also and it decreasing back to
minimum.

In tomcat I configured max threads 300.

context.xml is

<Context path="" reloadable="true">
<Resource
accessToUnderlyingConnectionAllowed="true"
auth="Container"
driverClassName="oracle.jdbc.OracleDriver"
  maxActive="200"
  maxIdle="10"
  maxWait="8000"
validationQuery="SELECT * from dual"
testOnBorrow="true"
removeAbandoned="true"
removeAbandonedTimeout="30"
logAbandoned="true"
name="jdbc/ds"
  password=""
type="javax.sql.DataSource"
  url=""
  username=""/>
<Resource auth="Container" name="mail/Session" type="javax.mail.Session"
mail.smtp.host="localhost"/>

</Context>

For few days I am getting this problem.