JDBC query hangs for 60 seconds

Question

Hi,
I'm trying to perform a series of very simple queries on a 8.1.7 database with jdk1.4 and ojdbc14 drivers. Every now and then, a query just hangs for exactly 60 seconds before continuing, without throwing any kind of exception. This sometimes happens after a couple of hundred queries, but it can also be after 4 or five. I thought maybe the database runs out of cursors, but then I would get an exception right? After every query, I close the ResultSet and Statement, so it should work just fine. When I tested the same program on PostgreSQL 7.2, it worked perfectly. Is this a problem with the Oracle JDBC drivers, or am I missing something?
Here's the code of my simple test app:
import java.sql.*;
import java.io.*;
class JdbcTest {
public static void main (String args []) throws Exception {
DriverManager.registerDriver (new oracle.jdbc.OracleDriver());
Connection conn = DriverManager.getConnection
("jdbc:oracle:thin:@foo.bar.com:1521:BLABLA","test", "test");
     for (int i=0;i<500;i++) {
     Statement stmt = conn.createStatement ();
     ResultSet rset = stmt.executeQuery ("SELECT sitenr,omschrijving FROM site");
     while (rset.next ())
          System.out.println (rset.getString (1) + ": " + rset.getString(2));
     rset.close();
     stmt.close();
conn.close();
}

Answer 1

Here's the thread dump:
"Signal Dispatcher" daemon prio=10 tid=0x009E8118 nid=0xdc4 waiting on condition
[0..0]
"Finalizer" daemon prio=9 tid=0x0003E6F0 nid=0xdd4 in Object.wait() [ab1f000..ab
1fd88]
at java.lang.Object.wait(Native Method)
- waiting on <02F81698> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:111)
- locked <02F81698> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:127)
at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:159)
"Reference Handler" daemon prio=10 tid=0x0003D2C0 nid=0xdd8 in Object.wait() [aa
df000..aadfd88]
at java.lang.Object.wait(Native Method)
- waiting on <02F81700> (a java.lang.ref.Reference$Lock)
at java.lang.Object.wait(Object.java:426)
at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:113)
- locked <02F81700> (a java.lang.ref.Reference$Lock)
"main" prio=5 tid=0x00034AB8 nid=0xdc8 runnable [7f000..7fc3c]
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at oracle.net.ns.Packet.receive(Unknown Source)
at oracle.net.ns.NetInputStream.getNextPacket(Unknown Source)
at oracle.net.ns.NetInputStream.read(Unknown Source)
at oracle.net.ns.NetInputStream.read(Unknown Source)
at oracle.net.ns.NetInputStream.read(Unknown Source)
at oracle.jdbc.ttc7.MAREngine.unmarshalUB1(MAREngine.java:931)
at oracle.jdbc.ttc7.MAREngine.unmarshalSB1(MAREngine.java:893)
at oracle.jdbc.ttc7.Oopen.receive(Oopen.java:105)
at oracle.jdbc.ttc7.TTC7Protocol.open(TTC7Protocol.java:586)
- locked <02FCA940> (a oracle.jdbc.ttc7.TTC7Protocol)
at oracle.jdbc.driver.OracleStatement.<init>(OracleStatement.java:385)
at oracle.jdbc.driver.OracleConnection.privateCreateStatement(OracleConn
ection.java:772)
at oracle.jdbc.driver.OracleConnection.createStatement(OracleConnection.
java:712)
- locked <02FCA890> (a oracle.jdbc.driver.OracleConnection)
at JdbcTest.main(JdbcTest.java:11)
"VM Thread" prio=5 tid=0x009E5030 nid=0xde0 runnable
"VM Periodic Task Thread" prio=10 tid=0x009E6E00 nid=0xdd0 waiting on condition
"Suspend Checker Thread" prio=10 tid=0x009E7750 nid=0xdcc runnable