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Oracle® Database Net Services Administrator's Guide
11g Release 1 (11.1)

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13 Enabling Advanced Features of Oracle Net Services

This chapter describes how to configure advanced features of Oracle Net Services, including advanced connect data parameters, load balancing, failover, and connections to non-database services.

This chapter contains these topics:

13.1 Configuring Advanced Network Address and Connect Data Information

This section contains the following advanced connect descriptor topics:

13.1.1 Creating a List of Listener Protocol Addresses

A database service may be accessed by more than one network route, or protocol address. In the following example, sales.us.example.com can connect to sales.us.example.com using listeners on either sales1-server or sales2-server.

sales.us.example.com=
 (DESCRIPTION=
  (ADDRESS_LIST=
    (ADDRESS=(PROTOCOL=tcp)(HOST=sales1-server)(PORT=1521))
    (ADDRESS=(PROTOCOL=tcp)(HOST=sales2-server)(PORT=1521)))
  (CONNECT_DATA=
    (SERVICE_NAME=sales.us.example.com)))

To add a network protocol address to an existing net service name or database service, use either Oracle Enterprise Manager or Oracle Net Manager.

Oracle Enterprise Manager

  1. Access the Directory Naming or Local Naming page in Oracle Enterprise Manager:

    1. Access the Net Services Administration page in Oracle Enterprise Manager.

    2. Select Local Naming or Directory Naming from the Administer list, and then select the Oracle home for the directory server or the location of the local configuration files.

    3. Click Go.

      The Directory Naming or Local Naming pages appear.

  2. Select the directory service or net service name.

    For Directory Naming, perform a search of the net service name in the Simple Search section, select the net service or database service from the Results list, and then click Edit. For Local Naming, select a net service from the list, and then click Edit.

  3. In the Addresses section, click Add.

    The Add Address page appears.

  4. From the Protocol list, select the protocol on which the listener is configured to listen. This protocol must also be installed on the client.

  5. Enter the appropriate parameter information for the selected protocol in the fields provided.

    See Also:

    Oracle Database Net Services Reference for protocol parameter settings
  6. Optionally, in the Advanced Parameters section, specify the I/O buffer space limit for send and receive operations of sessions in the Total Send Buffer Size and Total Receive Buffer Size fields.

    See Also:

    "Configuring I/O Buffer Space" for further information
  7. Click OK.

    The protocol address is added to the Addresses section.

  8. Click OK to update the address information.

Oracle Net Manager

  1. Start Oracle Net Manager.

  2. In the navigator pane, expand Directory or Local > Service Naming.

  3. Select either the net service name or a database service.

    The right pane displays the current destination service and address list.

  4. In the Address Configuration box, click plus (+) to add a new address.

    A new Address tab appears:

    1. Select the protocol and enter appropriate address information.

      See Also:

      Oracle Database Net Services Reference for details about protocol address parameters
    2. Optionally, on the Address tab, click Advanced to specify the I/O buffer space limit for send and receive operations of sessions in the Total Send Buffer Size and Total Receive Buffer Size fields.

      See Also:

      "Configuring I/O Buffer Space" for further information
    3. Order the protocol addresses according to where they should be in the protocol address list with the left-arrow and right-arrow buttons. Unless multiple address options are configured, the first address in the list is contacted.

      See Also:

      "Configuring Address List Parameters" for address list options
  5. If you are making these changes to the Local folder, then choose File > Save Network Configuration.

13.1.2 Configuring Address List Parameters

When a database service is accessible by multiple listener protocol addresses, specify the order in which the addresses are to be used. The addresses can be chosen randomly or tried sequentially.

When multiple protocol addresses have been configured for a net service name or database service, you can configure the parameters described in Table 13-1.

Table 13-1 Address List Parameters

Parameter Description

SOURCE_ROUTE (Source Routing)

When set to on, instructs Oracle Net to use each address in the order presented until the destination is reached. This parameter is required for reaching the destination using a specific route, that is, by specific computers. This parameter is used to enable connections to Oracle Connection Manager.

See Also: "Configuring Clients for Oracle Connection Manager"

FAILOVER (Connect-Time Failover)

At connect time, instructs Oracle Net to fail over to a different listener if the first listener fails when set to on. The number of addresses in the list determines how many addresses are tried. When set to off, instructs Oracle Net to try one address.

Connect-time failover is turned on by default for multiple address lists (ADDRESS_LIST), connect descriptors (DESCRIPTION), and multiple connect descriptors (DESCRIPTION_LIST).

Important:

When using a connect descriptor with a SERVICE_NAME, ensure that the value is neither a GLOBAL_DBNAME in any SID_DESC entry, nor a SID_NAME in any SID_DESC entry without a GLOBAL_DBNAME set.

LOAD_BALANCE (Client Load Balancing)

When set to on, instructs Oracle Net to progress through the list of protocol addresses in a random sequence, balancing the load on the various listeners. When set to off, instructs Oracle Net to try the addresses sequentially until one succeeds.

Client load balancing is turned on by default for multiple connect descriptors (DESCRIPTION_LIST).


Note:

It is not possible to set client load balancing or connect-time failover with source routing. While connect-time failover and client load balancing select an address from a list, source routing connects to each address in the list sequentially.

Source routing involves other configuration that goes beyond the scope of this section.

See Also:

"Configuring Clients for Oracle Connection Manager" for more information about configuring clients for source routing

To configure connect-time failover or client load balancing:

  1. Perform the procedure in "Creating a List of Listener Protocol Addresses".

  2. Use either Oracle Enterprise Manager or Oracle Net Manager to configure address list options.

    For Oracle Enterprise Manager, select the appropriate option in the Connect-time Failover and Client Load Balancing section.

    For Oracle Net Manager, click Advanced in the Address Configuration box. The Address List Options dialog box appears. Select the appropriate option.

    Table 13-2 describes the address list options.

Table 13-2 Address List Options Dialog Box

Option Parameter Setting

Try each address, in order, until one succeeds

FAILOVER=on

Try each address, randomly, until one succeeds

Note: This option is not enabled if Use Options Compatible with Net8 8.0 Clients is selected in Oracle Net Manager.

LOAD_BALANCE=on

FAILOVER=on

Try one address, selected at random

Note: This option is not enabled if Use Options Compatible with Net8 8.0 Clients is selected in Oracle Net Manager.

LOAD_BALANCE=on

Use each address in order until destination reached

SOURCE_ROUTE=on

Use only the first address

Note: This option is not enabled if Use Options Compatible with Net8 8.0 Clients is selected in Oracle Net Manager.

LOAD_BALANCE=off

FAILOVER=off

SOURCE_ROUTE=off


The following example shows a tnsnames.ora file configured for client load balancing:

sales.us.example.com=
 (DESCRIPTION=
  (ADDRESS_LIST=
  (LOAD_BALANCE=on)
   (ADDRESS=(PROTOCOL=tcp)(HOST=sales1-server)(PORT=1521)) 
   (ADDRESS=(PROTOCOL=tcp)(HOST=sales2-server)(PORT=1521)))
  (CONNECT_DATA=
    (SERVICE_NAME=sales.us.example.com))) 

The following example shows a tnsnames.ora file configured for connect-time failover:

sales.us.example.com=
 (DESCRIPTION=
  (ADDRESS_LIST=
   (LOAD_BALANCE=off)
   (FAILOVER=ON)
   (ADDRESS=(PROTOCOL=tcp)(HOST=sales1-server)(PORT=1521)) 
   (ADDRESS=(PROTOCOL=tcp)(HOST=sales2-server)(PORT=1521)))
  (CONNECT_DATA=(SERVICE_NAME=sales.us.example.com)))

13.1.3 Configuring Advanced Connect Data Parameters

The CONNECT_DATA section of a connect descriptor defines the destination database service. In the following example, SERVICE_NAME defines a service called sales.us.example.com:

sales.us.example.com=
 (DESCRIPTION=
   (ADDRESS=(PROTOCOL=tcp)(HOST=sales-server)(PORT=1521))
   (CONNECT_DATA=
    (SERVICE_NAME=sales.us.example.com))) 

Besides the service name, you can optionally configure the connect data information with the parameters described in Table 13-3.

Table 13-3 Advanced Connect Data Settings

Oracle Enterprise Manager/Oracle Net Manager Option tnsnames.ora File Parameter Description

Instance Name

INSTANCE_NAME

Used to identify the database instance to access.

The instance name can be obtained from the INSTANCE_NAME parameter in the initialization parameter file.

Note: This parameter is not enabled if Use Oracle8i Release 8.0 Compatible Identification is checked.

See Also: "About Connect Descriptors"

Session Data Unit Size

SDU

To optimize the transfer rate of data packets being sent across the network, you can specify the session data unit (SDU) size to change the performance characteristics having to do with the packets sent across the network.

See Also: "Configuring Session Data Unit"

Use for Heterogeneous Services

HS

If you want an Oracle database server to access a non-Oracle system through Heterogeneous Services, turn this option on.

See Also: "Configuring Oracle Net Services for Oracle Heterogeneous Services"

Oracle Rdb Settings

 

 

Oracle RDB Database

RDB_DATABASE

Specify the file name of the Oracle Rdb database.

See Also: "Configuring Oracle Net Services for an Oracle Rdb Database"

Type of Service

TYPE_OF_SERVICE

Specify the type of service to use for the Oracle Rdb database.

See Also: "Configuring Oracle Net Services for an Oracle Rdb Database"

Global Database Name

GLOBAL_NAME

Use to identify an Oracle Rdb database.

See Also: "Configuring Oracle Net Services for an Oracle Rdb Database"


To configure advanced CONNECT_DATA parameters for either a net service name or a database service:

To add a network protocol address to an existing net service name or database service, use either Oracle Enterprise Manager or Oracle Net Manager.

Oracle Enterprise Manager

  1. Access the Directory Naming or Local Naming page in Oracle Enterprise Manager:

    1. Access the Net Services Administration page in Oracle Enterprise Manager.

    2. Select Local Naming or Directory Naming from the Administer list, and then select the Oracle home for the directory server or the location of the local configuration files.

    3. Click Go.

      The Directory Naming or Local Naming pages appear.

  2. Select the directory service or net service name.

    For Directory Naming, perform a search of the net service name in the Simple Search section, select the net service or database service from the Results list, and then click Edit. For Local Naming, select a net service from the list, and then click Edit.

  3. Click the Advanced tab.

  4. Enter fields or select options as appropriate, and then click OK.

    See Also:

    Table 13-3, "Advanced Connect Data Settings" for a description of the fields and options
  5. Click OK to update the connect data information.

Oracle Net Manager

  1. Start Oracle Net Manager.

  2. In the navigator pane, expand Directory or Local > Service Naming.

  3. Select either the net service name or a database service.

    The right pane displays the current destination service and address list.

  4. In the Service Identification box, click Advanced.

    The Advanced Service Options dialog box appears.

    See Also:

    Table 13-3, "Advanced Connect Data Settings" for a description of the fields and options
  5. Enter fields or select options as appropriate, and then click OK.

  6. If you are making these changes to the Local folder, choose File > Save Network Configuration.

13.2 Configuring Connection Load Balancing

The connection load balancing feature improves connection performance by balancing the number of active connections among multiple dispatchers. In an Oracle Real Application Clusters environment, connection pool load balancing also has the capability to balance the number of active connections among multiple instances.

Because the PMON process can register with remote listeners, a listener can always be aware of all instances and dispatchers, regardless of their location. Depending on the load information, a listener decides which instance and, if shared server is configured, which dispatcher to send the incoming client request to.

In a shared server configuration, a listener selects a dispatcher in the following order: 1) least loaded node, 2) least loaded instance, and 3) least loaded dispatcher for that instance. In a dedicated server configuration, a listener selects an instance in the following order: 1) least loaded node, and 2) least loaded instance.

If a database service has multiple instances on multiple nodes, the listener selects the least loaded instance on the least loaded node. If shared server is configured, then the least loaded dispatcher of the selected instance is chosen.

An Oracle9i Real Application Clusters environment requires that the dispatchers on each instance be cross registered with the other listeners on the other nodes. This is achieved by the use of the LISTENER attribute of the DISPATCHERS parameter.

See Also:

Note:

For optimum connection pool load balancing results, the instances that belong to the same database service should be on equivalent hardware and software configurations.

This section includes the following two examples:

13.2.1 Example: Connection Pool Load Balancing for Shared Server Configuration

Figure 13-1 shows an Oracle Real Application Clusters shared server database with two instances, sales1 and sales2, of the same service, sales.us.example.com. The instances sales1 and sales2 reside on computers sales1-server and sales2-server, respectively. sales1 has one dispatcher and sales2 has two dispatchers. Listeners named listener run on nodes 1 and 2, respectively. The listener attribute in the DISPATCHERS parameter has been configured to allow for service registration of information to both listeners.

Figure 13-1 Load Balancing Environment for a Shared Server Configuration

Description of Figure 13-1 follows
Description of "Figure 13-1 Load Balancing Environment for a Shared Server Configuration"

The listeners_sales value in (LISTENER=listeners_sales) can be then resolved through a local tnsnames.ora file on the both servers as follows:

listeners_sales= 
 (DESCRIPTION= 
   (ADDRESS=(PROTOCOL=tcp)(HOST=sales1-server)(PORT=1521))
   (ADDRESS=(PROTOCOL=tcp)(HOST=sales2-server)(PORT=1521)))

Based on the environment, the following actions occur. The numbered actions correspond to the arrows shown in Figure 13-2:

  1. PMON processes for instances sales1 and sales2 register with both listeners. The listeners are updated on the load of the instances and dispatchers dynamically. The following load information is registered:

    The one minute load average for each instance is 600 for sales1 and 400 for sales2.

    The number of connections to each instance is 200 for sales1 and 300 for sales2.

    The number of dispatcher connections to each instance is 200 for dispatcher1, 100 for dispatcher2, and 200 for dispatcher3.

    The load average on sales2-server (400) is less than the load average on sales1-server (600). This can happen if more processing is required on sales1-server. The number of connections to sales1 (200) is the same as that of its only dispatcher, dispatcher1. The number of connections on sales2 (300) is the sum of the connections on its two dispatchers, dispatcher2 (100) and dispatcher 3 (200). Therefore, sales2 has more connections than sales1. In this example, sales2-server is the least loaded node, sales2 is the least loaded instance, and dispatcher2 is the least loaded dispatcher.

  2. The client sends a connect request.

    A connect descriptor is configured to try each protocol address randomly until one succeeds:

    sales.us.example.com= 
     (DESCRIPTION= 
      (LOAD_BALANCE=on)
      (FAILOVER=on)
      (ADDRESS=(PROTOCOL=tcp)(HOST=sales1-server)(PORT=1521))
      (ADDRESS=(PROTOCOL=tcp)(HOST=sales2-server)(PORT=1521))
      (CONNECT_DATA=(SERVICE_NAME=sales.us.example.com)))
    

    The listener on sales1-server was randomly chosen to receive the client connect request.

    The listener on sales1-server compares the load of the instances sales1 and sales2. The comparison takes into account the load on nodes sales1-server and sales2-server, respectively. Since sales2-server is less loaded than sales1-server, the listener selects sales2-server over sales1-server.

  3. The listener compares the load on dispatchers dispatcher2 and dispatcher3. Because dispatcher2 is less loaded than dispatcher3, the listener redirects the client connect request to dispatcher2.

  4. The client connects directly to dispatcher2.

Figure 13-2 Load Balancing Example for a Shared Server Configuration

Description of Figure 13-2 follows
Description of "Figure 13-2 Load Balancing Example for a Shared Server Configuration"

13.2.2 Example: Connection Pool Load Balancing for Dedicated Server Configuration

Figure 13-3 shows an Oracle Real Application Clusters dedicated server database with two instances, sales1 and sales2, of the same service, sales.us.example.com. The instances sales1 and sales2 reside on computers sales1-server and sales2-server, respectively. Listeners named listener run on nodes 1 and 2, respectively. The REMOTE_LISTENER parameter has been configured to allow for service registration of information to both listeners.

Figure 13-3 Load Balancing Environment for a Dedicated Server Configuration

Description of Figure 13-3 follows
Description of "Figure 13-3 Load Balancing Environment for a Dedicated Server Configuration"

The listener_sales2 value in (REMOTE_LISTENER=listener_sales2) can be then resolved through a local tnsnames.ora file on the sales1-server as follows:

listener_sales2= 
 (DESCRIPTION= 
   (ADDRESS=(PROTOCOL=tcp)(HOST=sales2-server)(PORT=1521)))

The listener_sales1 value in (REMOTE_LISTENER=listener_sales1) can be then resolved through a local tnsnames.ora file on the sales2-server as follows:

listener_sales1= 
 (DESCRIPTION= 
   (ADDRESS=(PROTOCOL=tcp)(HOST=sales1-server)(PORT=1521)))

Based on the environment, the following actions occur. The numbered actions correspond to the arrows shown in Figure 13-4:

  1. PMON processes for instances sales1 and sales2 register with both listeners. The listeners are updated on the load of the instances dynamically. The load information in Table 13-4 is registered:

    Table 13-4 Instance Load Information Upon Which Listeners are Updated

    Server or Instance 1 Minute Node Load Average Number of Connections to Instance

    sales1-server

    450

     

    sales2-server

    200

     

    sales1

     

    200

    sales2

     

    150


    In Table 13-4, sales2-server is the least loaded node and sales2 is the least loaded instance.

  2. The client sends a connect request.

    A connect descriptor is configured to try each protocol address randomly until one succeeds:

    sales.us.example.com= 
     (DESCRIPTION= 
      (LOAD_BALANCE=on)
      (FAILOVER=on)
      (ADDRESS=(PROTOCOL=tcp)(HOST=sales1-server)(PORT=1521))
      (ADDRESS=(PROTOCOL=tcp)(HOST=sales2-server)(PORT=1521))
      (CONNECT_DATA=(SERVICE_NAME=sales.us.example.com)))
    

    The listener on sales1-server was randomly chosen to receive the client connect request.

    The listener on sales1-server compares the load of the instances sales1 and sales2. The comparison takes into account the load on nodes sales1-server and sales2-server, respectively. Since sales2-server is less loaded than sales1-server, the listener selects sales2-server over sales1-server.

  3. The listener on sales1-server redirects the client connect request to the listener on sales2-server.

  4. The client connects to the listener on sale2-server. The listener starts a dedicated server process, and the dedicated server process inherits the connection request from the listener.

Figure 13-4 Load Balancing Example for a Dedicated Server Configuration

Description of Figure 13-4 follows
Description of "Figure 13-4 Load Balancing Example for a Dedicated Server Configuration"

13.3 Configuring Transparent Application Failover

Note:

Transparent Application Failover (TAF) is available with Oracle Database 11g Enterprise Edition.

TAF instructs Oracle Net to fail over a failed connection to a different listener. This enables the user to continue to work using the new connection as if the original connection had never failed.

TAF involves manual configuration of a net service name that includes the FAILOVER_MODE parameter included in the CONNECT_DATA section of the connect descriptor.

This sections covers the following topics:

13.3.1 About TAF

Transparent Application Failover (TAF) is a client-side feature that allows for clients to reconnect to surviving databases in the event of a failure of a database instance. Notifications are used by the server to trigger TAF callbacks on the client-side.

TAF is configured using either client-side specified TNS connect string or using server-side service attributes. However, if both methods are used to configure TAF, the server-side service attributes will supersede the client-side settings. The server-side service attributes are the preferred way to set up TAF.

TAF can operate in one of two modes, Session Failover and Select Failover. Session Failover will re-create lost connections and sessions. Select Failover will replay queries that were in progress.

When there is a failure, callback functions will be initiated on the client-side by means of OCI callbacks. This will work with standard OCI connections as well as Connection Pool and Session Pool connections. Please see the OCI manual for more details on callbacks, Connection Pools, and Session Pools.

TAF will work with RAC. For more details and recommended configurations, please see the RAC Administration Guide.

TAF will operate with Physical Data Guard to provide automatic failover.

13.3.2 What TAF Restores

TAF automatically restores some or all of the following elements associated with active database connections. Other elements, however, may need to be embedded in the application code to enable TAF to recover the connection.

13.3.2.1 Client-Server Database Connections

TAF automatically reestablishes the connection using the same connect string or an alternate connect string that you specify when configuring failover.

13.3.2.2 Users' Database Sessions

TAF automatically logs a user in with the same user ID as was used prior to failure. If multiple users were using the connection, then TAF automatically logs them in as they attempt to process database commands. Unfortunately, TAF cannot automatically restore other session properties. These properties can, however, be restored by invoking a callback function.

13.3.2.3 Executed Commands

If a command was completely executed upon connection failure, and it changed the state of the database, TAF does not resend the command. If TAF reconnects in response to a command that may have changed the database, TAF issues an error message to the application.

13.3.2.4 Open Cursors Used for Fetching

TAF allows applications that began fetching rows from a cursor before failover to continue fetching rows after failover. This is called "select" failover. It is accomplished by re-executing a SELECT statement using the same snapshot, discarding those rows already fetched and retrieving those rows that were not fetched initially. TAF verifies that the discarded rows are those that were returned initially, or it returns an error message.

13.3.2.5 Active Transactions

Any active transactions are rolled back at the time of failure because TAF cannot preserve active transactions after failover. The application instead receives an error message until a ROLLBACK is submitted.

13.3.2.6 Server-Side Program Variables

Server-side program variables, such as PL/SQL package states, are lost during failures; TAF cannot recover them. They can be initialized by making a call from the failover callback.

13.3.3 TAF Database Configurations

TAF works with the following database configurations to effectively mask a database failure:

13.3.4 FAILOVER_MODE Parameters

The FAILOVER_MODE parameter must be included in the CONNECT_DATA section of a connect descriptor. FAILOVER_MODE can contain the subparameters described in Table 13-5.

Table 13-5 Subparameters of the FAILOVER_MODE Parameter

FAILOVER_MODE Subparameter Description

BACKUP

Specify a different net service name for backup connections. A backup should be specified when using preconnect to pre-establish connections.

TYPE

Specify the type of failover. Three types of Oracle Net failover functionality are available by default to Oracle Call Interface (OCI) applications:

  • session: Set to failover the session. If a user's connection is lost, a new session is automatically created for the user on the backup. This type of failover does not attempt to recover selects.

  • select: Set to enable users with open cursors to continue fetching on them after failure. However, this mode involves overhead on the client side in normal select operations.

  • none: This is the default. No failover functionality is used. This can also be explicitly specified to prevent failover from happening.

METHOD

Determines how fast failover occurs from the primary node to the backup node:

  • basic: Set to establish connections at failover time. This option requires almost no work on the backup server until failover time.

  • preconnect: Set to pre-established connections. This provides faster failover but requires that the backup instance be able to support all connections from every supported instance.

RETRIES

Specify the number of times to attempt to connect after a failover. If DELAY is specified, RETRIES defaults to five retry attempts.

Note: If a callback function is registered, then this subparameter is ignored.

DELAY

Specify the amount of time in seconds to wait between connect attempts. If RETRIES is specified, DELAY defaults to one second.

Note: If a callback function is registered, then this subparameter is ignored.


Note:

Oracle Net Manager does not provide support for TAF parameters. These parameters must be manually added.

13.3.5 TAF Implementation

Important:

Do not set the GLOBAL_DBNAME parameter in the SID_LIST_listener_name section of the listener.ora. A statically configured global database name disables TAF.

Depending on the FAILOVER_MODE parameters, you can implement TAF in a number of ways. Oracle recommends the following methods:

13.3.5.1 Example: TAF with Connect-Time Failover and Client Load Balancing

Implement TAF with connect-time failover and client load balancing for multiple addresses. In the following example, Oracle Net connects randomly to one of the protocol addresses on sales1-server or sales2-server. If the instance fails after the connection, the TAF application fails over to the other node's listener, reserving any SELECT statements in progress.

sales.us.example.com=
 (DESCRIPTION=
  (LOAD_BALANCE=on) 
  (FAILOVER=on) 
  (ADDRESS=
       (PROTOCOL=tcp)  
       (HOST=sales1-server)  
       (PORT=1521)) 
  (ADDRESS=
       (PROTOCOL=tcp)  
       (HOST=sales2-server)  
       (PORT=1521)) 
  (CONNECT_DATA=
     (SERVICE_NAME=sales.us.example.com) 
     (FAILOVER_MODE=
       (TYPE=select) 
       (METHOD=basic))))

13.3.5.2 Example: TAF Retrying a Connection

TAF also provides the ability to automatically retry connecting if the first connection attempt fails with the RETRIES and DELAY parameters. In the following example, Oracle Net tries to reconnect to the listener on sales1-server. If the failover connection fails, Oracle Net waits 15 seconds before trying to reconnect again. Oracle Net attempts to reconnect up to 20 times.

sales.us.example.com=
 (DESCRIPTION=
  (ADDRESS=
       (PROTOCOL=tcp)  
       (HOST=sales1-server)  
       (PORT=1521)) 
  (CONNECT_DATA=
     (SERVICE_NAME=sales.us.example.com) 
     (FAILOVER_MODE=
       (TYPE=select) 
       (METHOD=basic)
       (RETRIES=20)
       (DELAY=15))))

13.3.5.3 Example: TAF Pre-Establishing a Connection

A backup connection can be pre-established. The initial and backup connections must be explicitly specified. In the following example, clients that use net service name sales1.us.example.com to connect to the listener on sales1-server are also preconnected to sales2-server. If sales1-server fails after the connection, Oracle Net fails over to sales2-server, preserving any SELECT statements in progress. Likewise, Oracle Net preconnects to sales1-server for those clients that use sales2.us.example.com to connect to the listener on sales2-server.

sales1.us.example.com=
 (DESCRIPTION=
  (ADDRESS=
       (PROTOCOL=tcp)  
       (HOST=sales1-server)  
       (PORT=1521)) 
  (CONNECT_DATA=
     (SERVICE_NAME=sales.us.example.com) 
     (INSTANCE_NAME=sales1) 
     (FAILOVER_MODE=
       (BACKUP=sales2.us.example.com) 
       (TYPE=select) 
       (METHOD=preconnect))))
sales2.us.example.com=
 (DESCRIPTION=
  (ADDRESS=
       (PROTOCOL=tcp)  
       (HOST=sales2-server)  
       (PORT=1521)) 
  (CONNECT_DATA=
     (SERVICE_NAME=sales.us.example.com) 
     (INSTANCE_NAME=sales2)
     (FAILOVER_MODE=
       (BACKUP=sales1.us.example.com) 
       (TYPE=select) 
       (METHOD=preconnect))))

13.3.6 TAF Verification

You can query FAILOVER_TYPE, FAILOVER_METHOD, and FAILED_OVER columns in the V$SESSION view to verify that TAF is correctly configured.

Use the V$SESSION view to obtain information about the connected clients and their TAF status. For example, query the FAILOVER_TYPE, FAILOVER_METHOD, and FAILED_OVER columns to verify that you have correctly configured TAF as in the following SQL statement:

SELECT MACHINE, FAILOVER_TYPE, FAILOVER_METHOD, FAILED_OVER, COUNT(*)
FROM V$SESSION
GROUP BY MACHINE, FAILOVER_TYPE, FAILOVER_METHOD, FAILED_OVER;

The output before failover resembles the following:

MACHINE              FAILOVER_TYPE FAILOVER_M FAI   COUNT(*)
-------------------- ------------- ---------- --- ----------
sales1               NONE          NONE       NO          11
sales2               SELECT        PRECONNECT NO           1

The output after failover is:

MACHINE              FAILOVER_TYPE FAILOVER_M FAI   COUNT(*)
-------------------- ------------- ---------- --- ----------
sales2               NONE          NONE       NO          10
sales2               SELECT        PRECONNECT YES          1

Note:

You can monitor each step of TAF using an appropriately configured OCI TAF CALLBACK function.

See Also:

13.4 Specifying the Instance Role for Primary and Secondary Instance Configurations

The INSTANCE_ROLE parameter is an optional parameter for the CONNECT_DATA section of a connect descriptor. It enables you to specify a connection to the primary or secondary instance of Oracle Real Application Clusters configurations.

This parameter is useful when:

INSTANCE_ROLE supports the following values:

primary — Specifies a connection to the primary instance

secondary — Specifies a connection to the secondary instance

any — Specifies a connection to whichever instance has the lowest load, regardless of primary or secondary instance role

Example: Connection to Instance Role Type

In the following example, net service name sales_primary enables connections to the primary instance, and net service name sales_secondary enables connections to the secondary instance.

sales_primary=
 (DESCRIPTION=
  (ADDRESS=
       (PROTOCOL=tcp)  
       (HOST=sales1-server)  
       (PORT=1521)) 
  (ADDRESS=
       (PROTOCOL=tcp)  
       (HOST=sales2-server)  
       (PORT=1521)) 
  (CONNECT_DATA=
     (SERVICE_NAME=sales.us.example.com) 
     (INSTANCE_ROLE=primary)))
sales_secondary=
 (DESCRIPTION=
  (ADDRESS=
       (PROTOCOL=tcp)  
       (HOST=sales1-server)  
       (PORT=1521)) 
  (ADDRESS=
       (PROTOCOL=tcp)  
       (HOST=sales2-server)  
       (PORT=1521)) 
  (CONNECT_DATA=
     (SERVICE_NAME=sales.us.example.com) 
     (INSTANCE_ROLE=secondary)))

Example: Connection To a Specific Instance

There are times when Oracle Enterprise Manager and other system management products need to connect to a specific instance regardless of its role to perform administrative tasks. For these types of connections, configure (INSTANCE_NAME=instance_name) and (INSTANCE_ROLE=any) to connect to the instance regardless of its role.

In the following example, net service name sales1 enables connections to the instance on sales1-server and sales2 enables connections to the instance on sales2-server. (SERVER=dedicated) is specified to force a dedicated server connection.

sales1=
 (DESCRIPTION=
  (ADDRESS=
       (PROTOCOL=tcp)  
       (HOST=sales1-server)  
       (PORT=1521)) 
  (CONNECT_DATA=
     (SERVICE_NAME=sales.us.example.com) 
     (INSTANCE_ROLE=any)
     (INSTANCE_NAME=sales2)
     (SERVER=dedicated)))
sales2=
 (DESCRIPTION=
  (ADDRESS=
       (PROTOCOL=tcp)  
       (HOST=sales2-server)  
       (PORT=1521)) 
  (CONNECT_DATA=
     (SERVICE_NAME=sales.us.example.com) 
     (INSTANCE_ROLE=any)
     (INSTANCE_NAME=sales2)
     (SERVER=dedicated)))

Example: TAF Pre-Establishing a Connection

If Transparent Application Failover (TAF) is configured, a backup connection can be pre-established to the secondary instance. The initial and backup connections must be explicitly specified. In the following example, Oracle Net connects to the listener on sales1-server and preconnects to sales2-server, the secondary instance. If sales1-server fails after the connection, the TAF application fails over to sales2-server, the secondary instance, preserving any SELECT statements in progress.

sales1.example.com=
 (DESCRIPTION=
  (ADDRESS=
       (PROTOCOL=tcp)  
       (HOST=sales1-server)  
       (PORT=1521)) 
  (CONNECT_DATA=
     (SERVICE_NAME=sales.us.example.com) 
     (INSTANCE_ROLE=primary) 
     (FAILOVER_MODE=
       (BACKUP=sales2.example.com) 
       (TYPE=select) 
       (METHOD=preconnect))))
sales2.example.com=
 (DESCRIPTION=
  (ADDRESS=
       (PROTOCOL=tcp)  
       (HOST=sales2-server)  
       (PORT=1521)) 
  (CONNECT_DATA=
     (SERVICE_NAME=sales.us.example.com) 
     (INSTANCE_ROLE=secondary)))

13.5 Configuring Connections to Non-Oracle Database Services

The following topics describe how to configure connections to non-Oracle database services:

13.5.1 Default Configuration for External Procedures

An external procedure is a procedure called from another program, but written in a different language. An example would be a PL/SQL program calling one or more C routines that are required to perform special-purpose processing.

When an application calls an external procedure, Oracle Database starts an external procedure agent named extproc. Using the network connection established by Oracle Database, the application passes the following information to the agent:

  • DLL or shared library name

  • External procedure name

  • Any parameters

The agent then loads the DLL or the shared library, and runs the external procedure and passes back to the application any values returned by the external procedure.

The agent must reside on the same computer as the application making the external procedure call.

Note:

The default configuration for external procedures no longer requires a network listener to work with Oracle Database and extproc agent. The extproc agent is spawned directly by Oracle Database and eliminates the risks that extproc might be spawned by Oracle Listener, unexpectedly. This default configuration is recommended for maximum security.

You can change the default configuration for external procedures and have your extproc agent spawned by Oracle Listener. To do this, however, you must perform additional network configuration steps.

Having your extproc agent spawned by Oracle Listener is necessary if you use:

  • Multi-threaded Agent

  • Oracle Database in MTS mode on Windows

  • AGENT clause of the LIBRARY specification or AGENT IN clause of the PROCEDURE specification such that you can redirect external procedures to a different extproc agent

When you use the default configuration for external procedures, the extproc agent is spawned directly by Oracle Database. There are no configuration changes required for either listener.ora or tnsnames.ora.

When the default configuration for external procedures is used, define the environment variables to be used by external procedures in the extproc.ora file located in the $ORACLE_HOME/hs/admin directory on UNIX operating systems or the %ORACLE_HOME%\hs\admin directory on Windows.

13.5.1.1 Configuring Oracle Net Services for External Procedures

You can change the default configuration for external procedures and have your extproc agent spawned by the listener similar to prior releases of Oracle Database.

To do this, modify the default configuration, as follows:

  1. Configure and run a separate or existing listener to serve external procedures.

    Oracle Net Configuration Assistant configures a listener to accept connections for both the database and external procedures during a database server installation. In addition, Oracle Net Configuration Assistant configures a net service name for the external procedures in tnsnames.ora file on the database server. The external procedure agent will only be able to load DLLS from the bin or lib directories in the ORACLE_HOME.

    Example 13-1 shows a sample configuration in the listener.ora file.

    Example 13-1 listener.ora File with a Sample External Procedure Setup

    LISTENER=
      (DESCRIPTION=
        (ADDRESS_LIST=
          (ADDRESS=(PROTOCOL=tcp)(HOST=sale-server)(PORT=1521))
          (ADDRESS=(PROTOCOL=ipc)(KEY=extproc))))
    SID_LIST_LISTENER=
      (SID_LIST=
        (SID_DESC=
          (GLOBAL_DBNAME=sales.us.example.com)
          (ORACLE_HOME=/oracle)
          (SID_NAME=sales))
        (SID_DESC=
          (SID_NAME=plsextproc)
          (ORACLE_HOME=/oracle)
          (PROGRAM=extproc)))
    

    Example 13-2 shows a sample configuration in the tnsnames.ora file.

    Example 13-2 tnsnames.ora File a Sample External Procedure Setup

    EXTPROC_CONNECTION_DATA=            
     (DESCRIPTION=                     
       (ADDRESS=(PROTOCOL=ipc)(KEY=extproc))                      
       (CONNECT_DATA=
        (SID=plsextproc)))
    

    The extproc agent spawned by the listener inherits the operating system privileges of the listener. Therefore, if you configure a separate listener, run with operating system privileges lower than those of the listener for the database.

  2. Restrict the DLLs that the extproc agent can load by listing them explicitly in the listener.ora file.

The details of these tasks follow.

To modify the default configuration for external procedures, configure and run a separate or existing listener to serve external procedures:

  1. To configure an existing listener to serve external procedures, choose the existing listener and configure it using Oracle Net Configuration Assistant.

    For most installation types, this listener is named LISTENER.

    1. Access the Oracle Net Administration page in Oracle Enterprise Manager.

    2. Select Listeners from the Administer list, and then select the Oracle home that contains the location of the configuration files.

    3. Click Go.

      The Listeners page appears.

    4. Select the existing listener created by Oracle Net Configuration Assistant, and then click Edit.

      The Edit Listeners page appears.

    5. In the Addresses section, select the protocol address for external procedures, and then click Add.

    6. Click the Other Services tab.

    7. Select the row representing the service information for external procedures, and then click Add.

  2. Add service information about extproc in the listener.ora file, including the parameters described in Table 13-6.

To configure and run a separate listener to serve external procedures, remove the external procedure entries for a different listener using Oracle Net Configuration Assistant.

  1. Create another listener to exclusively handle external procedures:

    1. Navigate back to the Listeners page.

    2. Click Create.

      The Create Listener page appears.

    3. In the Listener Name field, enter a unique listener name, such as LISTENEREXTPROC, in the Listener Name field.

  2. In the Addresses section, configure an IPC protocol address.

    1. Click Add.

      The Add Address page appears.

    2. From the Protocol list, select IPC.

    3. In the Key field, enter a key value of extproc.

      See Also:

      "Configuring Listening Protocol Addresses" for more information about configuring listener protocol addresses
    4. Click OK.

  3. Add service information about extproc in the listener.ora file, including the parameters described in Table 13-6.

Table 13-6 External Procedures Settings in listener.ora

Oracle Enterprise Manager Field listener.ora Parameter Description

Program Name

PROGRAM

Specify the name of the external procedure agent executable.

Note: On Windows, the executable must reside in the ORACLE_HOME\bin directory.

Environment Variables

ENVS

When the default configuration for external procedures is used, define the environment variables to be used by external procedures in the extproc.ora file located in the $ORACLE_HOME/hs/admin directory on UNIX operating sytems or the %ORACLE_HOME%\hs\admin directory on Windows.

Note: When extproc.ora is in use, it precedes the same environment variables of ENVS in listener.ora.

Syntax: SET name=value

Example: SET EXTPROC_DLLS=ANY

Specify the EXTPROC_DLLS environment variable to restrict the DLLs that extproc is allowed to load. Without the EXTPROC_DLLS environment variable, extproc loads DLLs from $ORACLE_HOME/lib on UNIX operating systems and ORACLE_HOME\bin on Windows.

Set EXTPROC_DLLS to one of the following values:

  • Colon-separated list of the DLLs

    Syntax: "DLL:DLL"

    Description: This value allows extproc to load the specified DLLs and the DLLs from $ORACLE_HOME/lib on UNIX operating systems and ORACLE_HOME\bin on Windows. You must enter the complete directory path and file name of the DLLs.

  • ONLY (Recommended for maximum security)

    Syntax: "ONLY:DLL:DLL"

    Description: This value allows extproc to load only the specified DLLs. You must enter the complete directory path and file name of the DLLs.

  • ANY

    Syntax: "ANY"

    Description: This value allows extproc to load any DLL. ANY disables DLL checking.

Examples:

"EXTPROC_DLLS=/home/xyz/mylib.so:/home/abc/urlib.so,LD_LIBRARY_PATH=/private/xpm/lib:/private/mylibs, 
MYPATH=/usr/ucb:/usr/local/packages,APL_ENV_FILE=/apl/conf/env.txt"

"EXTPROC_DLLS=ONLY:/home/xyz/mylib.so:/home/abc/urlib.so,LD_LIBRARY_PATH=/private/xpm/lib:/private/mylibs, 
MYPATH=/usr/ucb:/usr/local/packages,APL_ENV_FILE=/apl/conf/env.txt"

"EXTPROC_DLLS=ANY,LD_LIBRARY_PATH=/private/xpm/lib:/private/mylibs, 
MYPATH=/usr/ucb:/usr/local/packages,APL_ENV_FILE=/apl/conf/env.txt"

Oracle Home Directory

ORACLE_HOME

Specify the Oracle home location of the agent.

SID

SID_NAME

Specify a system identifier for the external procedure agent by any name.


To configure service information about extproc:

  1. Click the Other Services tab.

  2. Click Add.

    The Create Other Service page appears.

  3. Enter extproc in the Program Name field, and the Oracle home where the extproc executable resides in the Oracle Home Directory field, and a system identifier, such as extproc, in the SID field.

  4. In the Environment Variables section, click Add Another Row.

  5. Enter the EXTPROC_DLLS environment variable in the Name field and the directory path and file name of the DLLs in the Value field.

  6. Click OK.

    The Create Listener page appears.

  7. Click OK to add the listener.

    The listener is added to the Listeners page.

    The listener.ora file updates with information for external procedures, as shown in the following output:

    LISTENEREXTPROC=
     (DESCRIPTION=
      (ADDRESS=
         (PROTOCOL=ipc)(KEY=extproc)))
    SID_LIST_LISTENEREXTPROC=
      (SID_LIST=
        (SID_DESC=
         (PROGRAM=extproc)
         (ENVS="EXTPROC_DLLS=ONLY:/home/xyz/mylib.so:/home/abc/urlib.so,
          LD_LIBRARY_PATH=/private/xpm/lib:/private/mylibs,
          MYPATH=/usr/ucb:/usr/local/packages,APL_ENV_FILE=/apl/conf/env.txt")
         (SID_NAME=extproc)
         (ORACLE_HOME=/oracle)))
    
  8. Start the listener for external procedures from a user account with lower privileges than the oracle user.

    Ensure that this user account does not have general access to oracle-owned files. Specifically, this user should not have permission to read or write to database files or to the Oracle server address space. In addition, this user should have read access to the listener.ora file, but must not have write access to it.

    Running the listener with lower privileges also prevents you from using Listener Control utility SET commands to alter the configuration of this listener in the listener.ora file. For this reason, Oracle recommends that you complete listener.ora file configuration prior to running the listener.

    See Also:

13.5.2 Configuring Oracle Net Services for Oracle Heterogeneous Services

Heterogeneous Services are an integrated component within the Oracle database server, and provides the generic technology for accessing non-Oracle systems from the Oracle database server. Heterogeneous Services enable you to:

  • Use Oracle SQL to transparently access data stored in non-Oracle systems as if the data resides within an Oracle database server

  • Use Oracle procedure calls to transparently access non-Oracle systems, services, or application programming interfaces (APIs), from your Oracle distributed environment

While Heterogeneous Services provides the generic technology in the Oracle database server, a Heterogeneous Service agent is required to access a particular non-Oracle system.

To initiate a connection to the non-Oracle system, the Oracle database server starts an agent process through the listener on the gateway. For the Oracle database server to be able to connect to the agent, perform the following steps:

  1. Configure the listener on the gateway to listen for incoming requests from the Oracle database server and spawn Heterogeneous Services agents by configuring the following parameters in the listener.ora file:

    • PROGRAM: Specify the name of the agent executable

    • ORACLE_HOME: Specify the Oracle home location of the agent executable

    • SID_NAME: Specify the Oracle System Identifier (SID)

  2. Configure the PROGRAM, ORACLE_HOME, and SID parameters in Oracle Enterprise Manager.

    Access the Oracle Net Administration page in Oracle Enterprise Manager.

  3. Select Listeners from the Administer list, and then select the Oracle home that contains the location of the configuration files.

  4. Click Go.

    The Listeners page appears.

  5. Select the listener created by Oracle Net Configuration Assistant, and then click Edit.

    The Edit Listeners page appears.

  6. In the Addresses section, select the protocol address for external procedures, and then click Remove.

  7. Click the Other Services tab.

  8. Click Add.

    The Create Other Service page appears.

  9. Enter the program name in the Program Name field that will be executed to create a gateway, the Oracle home where the agent executable resides in the Oracle Home Directory field, and the SID or service name of the non-Oracle system in the SID field.

  10. Click OK.

    The Edit Listener page appears.

  11. Click OK to modify the listener.

    The Listeners page appears.

    The listener.ora file updates information about the Heterogeneous Services, as shown in the following:

    SID_LIST_LISTENER=
     (SID_LIST=
      (SID_DESC=
       (SID_NAME=sybasegw)
       (ORACLE_HOME=/oracle10g)
       (PROGRAM=tg4sybs)))
    
  12. On the computer where the Oracle database resides, set up a net service name to connect to the listener on the gateway. The connect descriptor must also include the HS=ok clause to make sure the connection uses Heterogeneous Services:

    1. Create a net service name that can be used for connections from the Oracle database server to a non-Oracle system.

      See Also:

      "Task 1: Configure Net Service Names" for local naming instructions and "Task 2: Create or Modify Net Entries" for directory naming instructions
    2. Use either Oracle Enterprise Manager or Oracle Net Manager to configure HS=ok.

      For Oracle Enterprise Manager, click the Advanced tab in the Create Net Service Name page, and then click the Use for Heterogeneous Services.

      For Oracle Net Manager, click Advanced in the Service Identification box. The Advanced Service Options dialog box appears. Click Use for Heterogeneous Services.

    3. Click OK to confirm the change.

      The tnsnames.ora file updates with the new net service name configured for Heterogeneous Services, as shown in the following:

      sybase_gtw=
       (DESCRIPTION=
        (ADDRESS=(PROTOCOL=tcp)(HOST=gate-server)(PORT=1521))
        (CONNECT_DATA=
          (SERVICE_NAME=sybasegw)
        )
          (HS=ok)))
       )
      

13.5.3 Configuring Oracle Net Services for an Oracle Rdb Database

Oracle Rdb is a database for Digital's 64-bit operating systems. Because Oracle Rdb has its own listener, the client interacts with Rdb in the same manner as it does with an Oracle database.

To initiate a connection to an Oracle Rdb, set up a net service name to connect to the Oracle Rdb database using the parameters described in Table 13-7.

Table 13-7 Oracle RDB Database Settings in a Connect Descriptor

Oracle Enterprise Manager Field tnsnames.ora Parameter Description

Rdb Database

RDB_DATABASE

Specify the file name of an Oracle Rdb database.

Type of Service

TYPE_OF_SERVICE

Specify the type of service to use for an Oracle Rdb database. It is used by Rdb interface tools. This feature should only be used if the application supports both Oracle Rdb and Oracle database services, and you want the application to load balance between the two.

Global Database Name

GLOBAL_NAME

(Optional) Specify the Oracle Rdb database.


See Also:

Oracle Rdb documentation

To configure a client for an Oracle Rdb database, use Oracle Net Manager:

  1. Create a net service name that can be used for connections from the Oracle server to a non-Oracle system.

    See Also:

    "Task 1: Configure Net Service Names" for local naming instructions and "Task 2: Create or Modify Net Entries" for directory naming instructions
  2. Use either Oracle Enterprise Manager or Oracle Net Manager to the Oracle Rdb parameters.

    For Oracle Enterprise Manager, click the Advanced tab in the Create Net Service Name page.

    For Oracle Net Manager, click Advanced in the Service Identification box. The Advanced Service Options dialog box appears.

  3. Enter the file name of an Oracle Rdb database in the Rdb Database field.

  4. Optionally, enter the global database name in the Global Database Name field, and, if needed, specify the type of service in the Type of Service field, and then click OK.

    The tnsnames.ora file updates with the new net service name configured for the Oracle Rdb database, as shown in the following:

    alpha5=
      (DESCRIPTION=
        (ADDRESS=...)
        (CONNECT_DATA=
          (SERVICE_NAME=generic)
          (RDB_DATABASE=[.mf]mf_personnel.rdb)
         (GLOBAL_NAME=alpha5)))
    

    In the following example, TYPE_OF_SERVICE is used to load balance between an Oracle Rdb database service and an Oracle database service:

    alpha5=
     (DESCRIPTION_LIST=
      (DESCRIPTION=
        (ADDRESS=...)
        (CONNECT_DATA=
         (SERVICE_NAME=generic)
         (RDB_DATABASE=[.mf]mf_personnel.rdb)
         (GLOBAL_NAME=alpha5)))
      (DESCRIPTION=
       (ADDRESS=...)
        (CONNECT_DATA=
         (SERVICE_NAME=sales.us.example.com))
       (TYPE_OF_SERVICE=oracle9_database))
    

    See Also:

    Oracle Rdb documentation