The Network Adapter could not establish the connection : Vendor code 20

Must Know

This error can be caused due to many issues like TNS listener is not responding or the max open sessions numbers exceeded, N/w sockets are hung/stuck issue. but usually I’ve seen its the issue with the listener service not running or hung state. Sometimes its gets clubbed with non responding DB.

Here in this case we received many different errors due to Listener not accepting new connections because it was in hung state and DB was non responsive with out of memory situation dur to some very long running queries which ate up memory over time. We thought restarting the DB and TNS listener should resolve this issue but doing that we faced many errors like below.

Error 1 - While Starting

SQL> startup;
ORA-01081: cannot start already-running ORACLE - shut it down first
SQL> shutdown immediate;
SP2-0640: Not connected
Database closed.
SP2-0640: Not connected
Database dismounted.
ORA-00600: internal error code, arguments: [kssadf_numa:  null parent], [], [], [], [], [], [], [], [], [], [], []
SQL> startup;
ORA-00000: normal, successful completion

Error 2 - While connecting to DB
An error was encountered performing the requested operation:

ORA-01033: ORACLE initialization or shutdown in progress
01033. 00000 -  "ORACLE initialization or shutdown in progress"
*Cause:    An attempt was made to log on while Oracle is being started up
or shutdown.
*Action:   Wait a few minutes. Then retry the operation.
Vendor code 1033

Error 3 -While starting/stopping TNS listener

lsnrctl start mydatabase11g

LSNRCTL for Linux: Version - Production on 27-MAR-2012 08:39:56

Copyright (c) 1991, 2010, Oracle.  All rights reserved.

TNS-01106: Listener using listener name mydatabase11g has already been started
Connecting to (ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROCmydatabase11g))
TNS-12541: TNS:no listener
TNS-12560: TNS:protocol adapter error
TNS-00511: No listener
Linux Error: 2: No such file or directory
Connecting to (ADDRESS=(PROTOCOL=TCP)(
TNS-12541: TNS:no listener
TNS-12560: TNS:protocol adapter error
TNS-00511: No listener
Linux Error: 111: Connection refused

So to cleanly restart the DB and Listener we did the following on the database hosting linux box.

Check if any stray outside applications connections are existing :

kill -9 `ps -ef|grep ORACLEUSER|grep LOCAL=NO|awk '{print $2}'`

The above command will kill any open connection which is not LOCAL.

type below commands to restart the DB.

sqlplus /nolog;

conn /as sysdba;

shutdown immediate;

Once shutdown completed. Use below commands


wait for the database to start and open for business.

Now check the TNS status by issuing below command:

lsnrctl status servicename

Ex: lsnrctl status mydatabase11g

If it gives errors then start the listener once again by issuing below command

lsnrctl start mydatabase11g

After command completion check the status once again and try connecting from out side.

Make sure it is able to connect and show you up time like below.

Start Date                27-MAR-2012 08:25:00
Uptime                    0 days 13 hr. 53 min. 33 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF

You can get the database connection details by issuing below command while logged in as sysdba also.

select instance_name,host_name,startup_time,status,database_status from v$instance;

If you need more info on starting and stopping a oracle database visit below url:

If you still see connectivity problems you may refer below urls to debug further:

In case of any ©Copyright or missing credits issue please check CopyRights page for faster resolutions.

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