Configuring Oracle Net Services

For Transparent Application Failover, you must configure Oracle Net Services by editing the tnsnames.ora and sqlnet.ora files on the Oracle database server.

Procedure

Locate the tnsnames.ora and sqlnet.orafiles in the network\admin directory of the Oracle home directory.
Note: These files do not exist in an Instant Client installation. In this case, you must create the files. These files must be in the same directory as one another. For example, you might choose to save these files in the Instant Client directory.
Open the files in a text editor.
Note: To configure Transparent Application Failover, you must use a text editor rather than Oracle Net Manager to edit these files.
Configure the files for your environment.

Example

The information in the following files is an example of how you can configure Transparent Application Failover:

sqlnet.ora:

SQLNET.AUTHENTICATION_SERVICES= (NONE)
NAMES.DIRECTORY_PATH= (TNSNAMES)

tnsnames.ora:

PRODONE =
(DESCRIPTION_LIST =
  (FAILOVER = true)
  (LOAD_BALANCE = false)
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = YourFirstHost)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVER = dedicated)
        (FAILOVER_MODE = 
           (BACKUP = PRODTWO)
           (TYPE = select)
           (METHOD = basic)
           (RETRIES = 20)
           (DELAY = 3)
        )
      (SERVICE_NAME = ORCL)
    )
  )
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = YourSecondHost)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVICE_NAME = ORCL)
    )
  )
)

PRODTWO =
(DESCRIPTION_LIST =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = YourSecondHost)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVICE_NAME = ORCL)
    )
  )
)

Note:

When you use Transparent Application Failover, if the connected instance fails or is shutdown, the adapter can automatically reconnect to a database. Transparent Application Failover enables the application to transparently reconnect to a specified secondary instance. This reconnection process creates a new connection that is identical to the original connection.
In the tnsnames.ora file, PRODONE is the example net service alias that defines both Transparent Application Failover and Connect Time Failover (CTF). The first description in the DESCRIPTION_LIST defines Transparent Application Failover. The second description in the DESCRIPTION_LIST defines Connect Time Failover.
The Transparent Application Failover description indicates that if an established connection to YourFirstHost fails, then the connection fails over to YourSecondHost via the PRODTWO net service alias. The Connect Time Failover description indicates that if YourFirstHost is down before the initial connection, then the connection fails over to YourSecondHost.
The select type is a feature of Transparent Application Failover. Use select to indicate that if the first connection fails while it is processing a SELECT statement, then the statement runs again when a new connection is established. The cursor moves to the correct position so the client can continue fetching rows without interruption.