3 round trips over network for simply "select sysdate from dual"

From: qihua wu <staywithpin_at_gmail.com>
Date: Fri, 20 Jun 2008 17:13:58 +0800
Message-ID: <2689c1070806200213q1f8195v8756ff0ca0496e42@mail.gmail.com>

Hi, all

When using tcpdump to check what happen over the network when do a simple query as
SQL> select sysdate from dual;

SYSDATE

---

20-JUN-08 The tcpdump is as following, 3 round trips between the server and client. Why so many trips? Don't we only need to 1 round trip as client send the query and the server reply?

16:56:13.354672 IP host1 > host2.1580: . 7898:8 054(156) ack 6755 win 32768
16:56:13.354683 IP host2.1580 > host1: . 6755:6 836(81) ack 8054 win 32768
16:56:13.521731 IP host1 > host2.1580: . 8054:8 126(72) ack 6836 win 32768
16:56:13.521744 IP host2.1580 > host1: . 6836:6 853(17) ack 8126 win 32768
16:56:13.688967 IP host1 > host2.1580: . 8126:8 141(15) ack 6853 win 32768
16:56:13.688980 IP host2.1580 > host1: . 6853:6 874(21) ack 8141 win 32768

And the expert says below: one additional roundtrip to initiate the query. Don't quite understand why we need additional roundtrip to initiate. http://www.adp-gmbh.ch/ora/sqlplus/arraysize.html

Thanks,
Qihua

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http://www.freelists.org/webpage/oracle-l Received on Fri Jun 20 2008 - 04:13:58 CDT