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SQL*Plus Connection Slow and May Yield ORA-03135: Connection Lost Contact (Doc ID 1639354.1)

Last updated on JANUARY 01, 2020

Applies to:

Oracle Net Services - Version and later
IBM AIX on POWER Systems (64-bit)
The problem documented here arose after a change to DNS. It describes a performance issue limited to connect time and does not address any other kinds of performance problems.


The following issue arose on an AIX server running 11gR2.

Following a change to the DNS configuration on this Unix host, the client can no longer establish a connection via the listener.  Additionally, connections that are attempted using the local or  BEQUEATH protocol are considerably slower.   

Here are the tests conducted and a description of the results:

1. Connect to the local instance via the BEQ protocol (without listener).
$ set ORACLE_SID=mysid
$ sqlplus / as sysdba 

Very slow to establish a connection but eventually successful

2. Attempt to connect to the local instance via the TCP listener and it will fail:

$ sqlplus myuser@TNS_Alias

SQL*Plus: Release Production on Wed Feb 26 14:24:46 2014

Copyright (c) 1982, 2011, Oracle.  All rights reserved.

ORA-03135: connection lost contact<=====Fails to connect with 'lost contact'
Process ID: 0
Session ID: 0 Serial number: 0

3. Oracle*Net Trace reveals the following:



4.   Nslookup run against the server's hostname yielded the correct results.

5.   Ifconfig -a command shows IPv6 was set on loopback interface lo0:

$ ifconfig -a
        inet netmask 0xffffff00 broadcast
         tcp_sendspace 131072 tcp_recvspace 65536 rfc1323 0
        inet netmask 0xff000000 broadcast

         inet6 ::1%1/0    <<===== Note the loopback interface configured with IPv6


The customer recently changed the DNS settings in /etc/netsvc.conf to:


This change would enable both IPv4 and IPv6 DNS searches. 


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