How do I restrict or allow a few client machines to connect to Oracle Server ?

If you do not want a particular client machine say machine of person X , connect to oracle server or vice versa.

The step are very simple , you need the following things

You must know the IP-address or host name of the client machine.

# Add the following lines in SQLNET.ora if you want to invite only the following client machine to connect
TCP.INVITED_NODES =(, )
# Add the following lines to SQLNET.ora if you want to invite all the client machine except the following
TCP.EXCLUDED_NODES=(, )
# The following is the required parameter in SQLNET.ora.
TCP.VALIDNODE_CHECKING=yes

Here is the simple example, to allows the user to connect to the oracle database with IP-ADDRESS 172.16.8.209 or 172.16.8.207 only , configure the protocol.ora as follows :-

tcp.invited_nodes=(172.16.8.209 , 172.16.8.207 )
tcp.validnode_checking=yes
Stop and restart the listener to make this effect.


Note : There are certian bugs attached with this method , check the oracle support or metalink for this for your specific platform and oracle version.
For further information check the metalink doc 185936.1