MacLochlainns Weblog

A student encountered a connection problem with a PHP application that failed to resolve to the database. The steps to validate this are to check the PHP credentials, which are in this older post. Once you’ve done that, you should do:

1. Check the tnsnames.ora file contents, they should have a hostname value not an IP address. When you’ve not set your machine hostname in Microsoft Windows host file (mine in the example is: McLaughlin7x64), Oracle opts for the IP address.

XE =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = McLaughlin7x64)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = xe)
    )
  )

2. Check if the Oracle TNS (Transparent Network Substrate) validates with this command:

tnsping xe

3. If the prior step fails, check to see if you’re listener is running and that it’s configuration file looks more or less like this sample. If it doesn’t, you should edit this listener.ora file and start the listener process through the services dialog.

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = McLaughlin7x64)(PORT = 1521))
    )
  )

4. You should then be able to connect like this:

sqlplus username/password@xe

Hope this helps a few people.