7
Local Naming Parameters (tnsnames.ora)

This chapter provides a complete listing of the tnsnames.ora file configuration parameters.

This chapter contains these topics:

Overview of Local Naming Parameters

This tnsnames.ora file is a configuration file that contains net service names mapped to connect descriptors for the local naming method, or net service names mapped to listener protocol addresses.

A net service name is an alias mapped to a database network address contained in a connect descriptor. A connect descriptor contains the location of the listener through a protocol address and the service name of the database to which to connect. Clients and database servers (that are clients of other database servers) use the net service name when making a connection with an application.

By default, tnsnames.ora is located in the $ORACLE_HOME/network/admin directory on UNIX operating systems and in the ORACLE_HOME\network\admin directory on Windows operating systems. tnsnames.ora can also be stored the following locations:

The directory specified by the TNS_ADMIN environment variable or registry value
On UNIX operating systems, the global configuration directory. For example, on the Solaris Operating System, this directory is /var/opt/oracle.

See Also:
Oracle operating system-specific documentation

General Syntax of tnsnames.ora

The basic syntax for a tnsnames.ora file is shown in Figure 7-1. DESCRIPTION contains the connect descriptor, ADDRESS contains the protocol address, and CONNECT_DATA contains the database service identification information.

Figure 7-1 Basic Format of tnsnames.ora File

net_service_name= 
 (DESCRIPTION= 
   (ADDRESS=(protocol_address_information))
   (CONNECT_DATA= 
     (SERVICE_NAME=service_name)))

Multiple Descriptions in tnsnames.ora

A tnsnames.ora file can contain net service names with one or more connect descriptors. Each connect descriptor can contain one or more protocol addresses. Figure 7-2 shows two connect descriptors with multiple addresses. DESCRIPTION_LIST defines a list of connect descriptors.

Note:

Oracle Net Manager does not support the creation of multiple connect descriptors for a net service name.

Figure 7-2 Net Service Name with Multiple Connect Descriptors in tnsnames.ora

net_service_name= 
 (DESCRIPTION_LIST=
  (DESCRIPTION= 
   (ADDRESS=(protocol_address_information))
   (ADDRESS=(protocol_address_information))
   (ADDRESS=(protocol_address_information))
   (CONNECT_DATA= 
     (SERVICE_NAME=service_name)))
  (DESCRIPTION= 
   (ADDRESS=(protocol_address_information))
   (ADDRESS=(protocol_address_information))
   (ADDRESS=(protocol_address_information))
   (CONNECT_DATA= 
     (SERVICE_NAME=service_name))))

Multiple Address Lists in tnsnames.ora

The tnsnames.ora file also supports connect descriptors with multiple lists of addresses, each with its own characteristics. In Figure 7-3, two address lists are presented. The first address list features client load balancing and no connect-time failover, affecting only those protocol adresses within the ADDRESS_LIST. The second protocol address list features connect-time failover and no client load loading balancing, affecting only those protocol addresses within the ADDRESS_LIST. The client first tries either the first or second protocol address at random, then tries protocol addresses three and four sequentially.

Note:

Oracle Net Manager supports only the creation of one protocol address list for a connect descriptor.

Figure 7-3 Multiple Address Lists in tnsnames.ora

net_service_name= 
 (DESCRIPTION= 
  (ADDRESS_LIST= 
   (LOAD_BALANCE=on)
   (FAILOVER=off)
   (ADDRESS=(protocol_address_information))
   (ADDRESS=(protocol_address_information)))
  (ADDRESS_LIST= 
   (LOAD_BALANCE=off)
   (FAILOVER=on)
   (ADDRESS=(protocol_address_information))
   (ADDRESS=(protocol_address_information)))
  (CONNECT_DATA=
   (SERVICE_NAME=service_name)))

Note:

Protocol address lists do not have to be embedded in an ADDRESS_LIST if there is only one list, as was the case prior to release 8.1.

Connect-Time Failover and Client Load Balancing with Oracle Connection Managers

When a connect descriptor in a tnsnames.ora file contains at least two protocol addresses for Oracle Connection Manager, parameters for connect-time failover and load balancing can be included in the file.

Figure 7-4 illustrates failover of multiple Oracle Connection Manager protocol addresses.

Figure 7-4 Multiple Oracle Connection Manager Addresses in tnsnames.ora

sample1=
 (DESCRIPTION= 
   (SOURCE_ROUTE=yes) 
   (ADDRESS=(PROTOCOL=tcp)(HOST=host1)(PORT=1630))    # hop 1 
   (ADDRESS_LIST=  
     (FAILOVER=on) 
     (LOAD_BALANCE=off)                                # hop 2 
     (ADDRESS=(PROTOCOL=tcp)(HOST=host2a)(PORT=1630)) 
     (ADDRESS=(PROTOCOL=tcp)(HOST=host2b)(PORT=1630)))
   (ADDRESS=(PROTOCOL=tcp)(HOST=host3)(PORT=1521))    # hop 3
   (CONNECT_DATA=(SERVICE_NAME=Sales.us.acme.com)))

In Figure 7-4:

The client is instructed to connect to an protocol address of the first Oracle Connection Manager, as indicated by:
```
(ADDRESS=(PROTOCOL=tcp)(HOST=host1)(PORT=1630))
```
The first Oracle Connection Manager is then instructed to connect to the first protocol address of another Oracle Connection Manager. If the first protocol address fails, then it tries the second protocol address. This sequence is specified with the following configuration:
```
(ADDRESS_LIST=  
  (FAILOVER=ON) 
  (LOAD_BALANCE=off)
  (ADDRESS=(PROTOCOL=tcp)(HOST=host2a)(PORT=1630)) 
  (ADDRESS=(PROTOCOL=tcp)(HOST=host2b)(PORT=1630)) 
```
The Oracle Connection Manager then connects to the database service using the following protocol address:
```
(ADDRESS=(PROTOCOL=tcp)(HOST=host3)(PORT=1521)) 
```

Figure 7-5 illustrates client load balancing among two Oracle Connection Managers and two protocol addresses:

Figure 7-5 Client Load Balancing in tnsnames.ora

sample2=
 (DESCRIPTION= 
   (LOAD_BALANCE=on) 
   (FAILOVER=on)
   (ADDRESS_LIST= 
     (SOURCE_ROUTE=yes) 
     (ADDRESS=(PROTOCOL=tcp)(HOST=host1)(PORT=1630)) 
     (ADDRESS=(PROTOCOL=tcp)(HOST=host2)(PORT=1521)))
  (ADDRESS_LIST= 
     (SOURCE_ROUTE=yes) 
     (ADDRESS=(PROTOCOL=tcp)(HOST=host3)(port=1630)) 
     (ADDRESS=(PROTOCOL=tcp)(HOST=host4)(port=1521)))
   (CONNECT_DATA=(SERVICE_NAME=sales.us.acme.com)))

In Figure 7-5:

The client is instructed to pick an ADDRESS_LIST at random and to failover to the other if the chosen ADDRESS_LIST fails. This is indicated by the LOAD_BALANCE and FAILOVER parameters being set to on.
When an ADDRESS_LIST is chosen, the client first connects to the Oracle Connection Manager, using the Oracle Connection Manager protocol address that uses port 1630 indicated for the ADDRESS_LIST.
The Oracle Connection Manager then connects to the database service, using the protocol address indicated for the ADDRESS_LIST.

Local Naming Parameters

This section lists and describes the tnsnames.ora file parameters that comprise connect descriptors. Configuration parameters fall into the following categories:

Connect Descriptor Descriptions

Each connect descriptor is contained within a DESCRIPTION parameter. Multiple connect descriptors are characterized by the DESCRIPTION_LIST parameter. These parameters are described next.

DESCRIPTION

Purpose

Use the DESCRIPTION parameter as a container for a connect descriptor.

Embed this parameter under the DESCRIPTION_LIST parameter.

Example

net_service_name=
(DESCRIPTION=
  (ADDRESS=...)
  (CONNECT_DATA=(SERVICE_NAME=sales.us.acme.com)))

DESCRIPTION_LIST

Purpose

Use he DESCRIPTION_LIST parameter defines a list of connect descriptors for a particular net service name.

Example

net_service_name= 
(DESCRIPTION_LIST=
 (DESCRIPTION=
  (ADDRESS=...)
  (CONNECT_DATA=(SERVICE_NAME=sales.acme.com)))
 (DESCRIPTION=
  (ADDRESS=...)
  (CONNECT_DATA=(SERVICE_NAME=sales2.us.acme.com))))

Protocol Address Section

The protocol address section of the tnsnames.ora file specifies the protocol addresses of the listener.

ADDRESS

Purpose

Use the parameter ADDRESS to define a single listener protocol address.

Embed this parameter under either the ADDRESS_LIST parameter or the DESCRIPTION parameter.

See Also:

Chapter 5, "Protocol Address Configuration" for descriptions of the correct parameters to use for each protocol

Example

net_service_name=
(DESCRIPTION= 
 (ADDRESS=(PROTOCOL=tcp)(HOST=sales-svr)(PORT=1521))
 (CONNECT_DATA=(SERVICE_NAME=sales.us.acme.com))

ADDRESS_LIST

Purpose

Use the parameter ADDRESS_LIST to define a list of protocol addresses. If there is only address list, ADDRESS_LIST is not necessary.

Embed this parameter under either the DESCRIPTION parameter or the DESCRIPTION_LIST parameter.

Example

net_service_name=
 (DESCRIPTION= 
  (ADDRESS_LIST=
   (ADDRESS=(PROTOCOL=tcp)(HOST=sales1-svr)(PORT=1521))
   (ADDRESS=(PROTOCOL=tcp)(HOST=sales2-svr)(PORT=1521)))
  (ADDRESS_LIST=
   (FAILOVER=on)
   (ADDRESS=(PROTOCOL=tcp)(HOST=sales1-svr)(PORT=1521))
   (ADDRESS=(PROTOCOL=tcp)(HOST=sales2-svr)(PORT=1521))
  (CONNECT_DATA=(SERVICE_NAME=sales.us.acme.com)))

Optional Parameters for Lists

For multiple addresses, the following parameters are available for usage:

FAILOVER

Purpose

Use the parameter FAILOVER to enable or disable connect-time failover for multiple protocol addresses.

When you set the parameter to on, yes, or true, Oracle Net, at connect time, fails over to a different address if the first protocol address fails. When you set the parameter to off, no, or false, Oracle Net tries one protocol address.

Embed this parameter under either the DESCRIPTION_LIST parameter, the DESCRIPTION parameter, or the ADDRESS_LIST parameter.

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 connect-time failover.

Default

on for DESCRIPTION_LISTs, DESCRIPTIONs, and ADDRESS_LISTs

Values

on | off | yes | no | true | false

Example

net_service_name=
 (DESCRIPTION= 
  (FAILOVER=on)
  (ADDRESS=(PROTOCOL=tcp)(HOST=sales1-svr)(PORT=1521))
  (ADDRESS=(PROTOCOL=tcp)(HOST=sales2-svr)(PORT=1521)))
  (CONNECT_DATA=(SERVICE_NAME=sales.us.acme.com)))

LOAD_BALANCE

Purpose

Use the parameter LOAD_BALANCE to enable or disable client load balancing for multiple protocol addresses.

When you set the parameter to on, yes, or true, Oracle Net progresses through the list of addresses in a random sequence, balancing the load on the various listener or Oracle Connection Manager protocol addresses. When you set the parameter to off, no, or false, Oracle Net tries the protocol addresses sequentially until one succeeds.

Embed this parameter under either the DESCRIPTION_LIST parameter, the DESCRIPTION parameter, or the ADDRESS_LIST parameter.

Default

on for DESCRIPTION_LISTs

Values

on | off | yes | no | true | false

Example

net_service_name=
 (DESCRIPTION= 
  (LOAD_BALANCE=on)
  (ADDRESS=(PROTOCOL=tcp)(HOST=sales1-svr)(PORT=1521))
  (ADDRESS=(PROTOCOL=tcp)(HOST=sales2-svr)(PORT=1521)))
  (CONNECT_DATA=(SERVICE_NAME=sales.us.acme.com))

SDU

Purpose

Use the parameter SDU to instruct Oracle Net to optimize the transfer rate of data packets being sent across the network with the session data unit (SDU) size you specify.

Embed this parameter under the DESCRIPTION parameter.

See Also:

Oracle9i Net Services Administrator's Guide for complete configuration information

Default

2 KB

Usage

The SDU size can range from 512 bytes to 32 KB. The default SDU for the client and the database is 2 KB.

Optimal SDU size depends on the maximum segment size (MSS) and message fragmentation. For Two-Task Common (TTC) connections, configuring an SDU size larger than the 2 KB default requires configuring the SDU on both the client and server computers. When the configured values do not match, the lower of the two values will be used.

To minimize packet header overhead and message fragmentation, set the SDU size as a multiple of the MSS. When Oracle Advanced Security encryption is not used, increase the SDU size by one (1). For example, the TCP/IP version 4 MSS on Ethernet is 1460 bytes. Use a multiple of 1460 for the SDU size if encryption is used. If encryption is not used, increase the SDU size to 1461.

Example

net_service_name= 
 (DESCRIPTION=
  (SDU=2920)
  (ADDRESS=...)
  (ADDRESS=...)
  (CONNECT_DATA=
    (SERVER_NAME=sales.us.acme.com))

SOURCE_ROUTE

Purpose

Use the parameter SOURCE_ROUTE to enable routing through multiple protocol addresses.

When you set to on or yes, Oracle Net uses each address in order until the destination is reached.

To use Oracle Connection Manager, an initial connection from the client to Oracle Connection Manager is required, and a second connection from Oracle Connection Manager to the listener is required.

Embed this parameter under either the DESCRIPTION_LIST parameter, the DESCRIPTION parameter, or the ADDRESS_LIST parameter.

See Also:

Oracle9i Net Services Administrator's Guide for complete configuration information

Default

off

Values

yes | no | on | off

Example

net_service_name=
 (DESCRIPTION= 
  (SOURCE_ROUTE=on)
  (ADDRESS=(PROTOCOL=tcp)(HOST=cman-pc)(PORT=1630))
  (ADDRESS=(PROTOCOL=tcp)(HOST=sales1-svr)(PORT=1521)))
  (CONNECT_DATA=(SERVICE_NAME=sales.us.acme.com))

TYPE_OF_SERVICE

Purpose

Use the parameter TYPE_OF_SERVICE parameter to specify the type of service to use for an Oracle Rdb database. This parameter should only be used if the application supports both an Oracle Rdb and Oracle database service, and you want the application to load balance between the two.

Embed this parameter under the DESCRIPTION parameter.

Example

net_service_name=
 (DESCRIPTION_LIST=
  (DESCRIPTION=
   (ADDRESS=...)
   (CONNECT_DATA= 
    (SERVICE_NAME=generic)
    (RDB_DATABASE=[.mf]mf_personal.rdb)
    (GLOBAL_NAME=alpha5))
   (TYPE_OF_SERVICE=rdb_database))
  (DESCRIPTION=
   (ADDRESS=...)
   (CONNECT_DATA=
    (SERVICE_NAME=sales.us.acme.com))
   (TYPE_OF_SERVICE=oracle9_database)))

Connect Data Section

The connection data section of the tnsnames.ora file specifies the name of the destination service.

CONNECT_DATA

Purpose

Use the parameter CONNECT_DATA to define the service to which to connect.

Embed this parameter under the DESCRIPTION parameter.

Usage Notes

CONNECT_DATA permits the following subparameters:

Example

net_service_name=
 (DESCRIPTION= 
  (ADDRESS=(PROTOCOL=tcp)(HOST=sales1-svr)(PORT=1521))
  (ADDRESS=(PROTOCOL=tcp)(HOST=sales2-svr)(PORT=1521))
  (CONNECT_DATA=
   (SERVICE_NAME=sales.us.acme.com)))

FAILOVER_MODE

Purpose

Use the parameter FAILOVER_MODE to instruct Oracle Net to fail over to a different listener if the first listener fails during runtime. Depending upon the configuration, session or any SELECT statements which were in progress are automatically failed over.

This type of failover is called Transparent Application Failover (TAF) and should not be confused with the connect-time failover FAILOVER parameter.

Embed this parameter under the CONNECT_DATA parameter.

See Also:

Oracle9i Net Services Administrator's Guide for complete configuration information

Subparameters

FAILOVER_MODE supports the following subparameters:

BACKUP: Specify the failover node by its net service name. A separate net service name must be created for the failover node.

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

session: Fails over the session; that is, 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: Allows 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, in which no failover functionality is used. This can also be explicitly specified to prevent failover from happening.

METHOD: Specify how fast failover is to occur from the primary node to the backup node:

basic: Establishes connections at failover time. This option requires almost no work on the backup database server until failover time.

preconnect: Pre-establishes 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.

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 RETRIES and DELAY subparameters are ignored.

Example

See Also:

Oracle9i Net Services Administrator's Guide for implementation examples

GLOBAL_NAME

Purpose

Use the parameter GLOBAL_NAME to identify the Oracle Rdb database.

Embed this parameter under the CONNECT_DATA parameter.

Example

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

HS

Purpose

Use the parameter HS to instruct Oracle Net to connect to a non-Oracle system through Heterogeneous Services.

Embed this parameter under the CONNECT_DATA parameter.

See Also:

Oracle9i Net Services Administrator's Guide for complete configuration information

Default

None

Values

ok

Example

net_service_name= 
 (DESCRIPTION=
   (ADDRESS=...)
   (ADDRESS=...)
   (CONNECT_DATA=
    (SID=sales6)
    (HS=ok)))

INSTANCE_NAME

Purpose

Use the parameter INSTANCE_NAME to identify the database instance to access. Set the value to the value specified by the INSTANCE_NAME parameter in the initialization parameter file.

Embed this parameter under the CONNECT_DATA parameter.

See Also:

Oracle9i Net Services Administrator's Guide for information about the use of INSTANCE_NAME

Example

net_service_name= 
 (DESCRIPTION=
   (ADDRESS=...)
   (ADDRESS=...)
   (CONNECT_DATA=
    (SERVICE_NAME=sales.us.acme.com)
    (INSTANCE_NAME=sales1)))

RDB_DATABASE

Purpose

Use the parameter RDB_DATABASE parameter to specify the file name of an Oracle Rdb database.

Embed this parameter under the CONNECT_DATA parameter.

Example

net_service_name= 
 (DESCRIPTION= 
   (ADDRESS=...)
   (ADDRESS=...)
   (CONNECT_DATA=
    (SERVICE_NAME=sales.us.acme.com)
    (RDB_DATABASE= [.mf]mf_personal.rdb)))

SERVER

Purpose

Use the parameter SERVER to instruct the listener to connect the client to a specific type of service handler.

Embed this parameter under the CONNECT_DATA parameter.

Values

dedicated to specify that client requests be served by dedicated server

shared to specify that client request be served by shared server

Note:

Shared server must be configured in the database initialization file in order for the client to connect to the database with a shared server process. See the Oracle9i Net Services Administrator's Guide for configuration information.

Note:

The USE_DEDICATED_SERVER parameter in the sqlnet.ora file overrides this parameter.

Example

net_service_name= 
 (DESCRIPTION=
   (ADDRESS=...)
   (ADDRESS=...)
   (CONNECT_DATA=
    (SERVER_NAME=sales.us.acme.com)
    (SERVER=dedicated)))

SERVICE_NAME

Purpose

Use the parameter SERVICE_NAME to identify the Oracle9i or Oracle8i database service to access. Set the value to a value specified by the SERVICE_NAMES parameter in the initialization parameter file.

Embed this parameter under the CONNECT_DATA parameter.

See Also:

Oracle9i Net Services Administrator's Guide for information about the use of the SERVICE_NAME parameter

Example

net_service_name= 
 (DESCRIPTION=
   (ADDRESS=...)
   (ADDRESS=...)
   (CONNECT_DATA=
    (SERVICE_NAME=sales.us.acme.com)))

SID

Purpose

Use the parameter SID to identify the Oracle8 database instance by its Oracle System Identifier (SID). If the database is Oracle9i or Oracle8i, use the SERVICE_NAME parameter rather than the SID parameter.

See Also:

Oracle9i Net Services Administrator's Guide for information about the use of SID

Embed this parameter under the CONNECT_DATA parameter.

Example

net_service_name= 
 (DESCRIPTION=
   (ADDRESS=...)
   (ADDRESS=...)
   (CONNECT_DATA=
    (SID=sales)))

Security Section

The security section of the tnsnames.ora file specifies security-related parameters for use with Oracle Advanced Security features.

SECURITY

Purpose

Use the parameter SECURITY to enable secure connections.

Embed this parameter under the DESCRIPTION parameter.

Usage Notes

SECURITY permits the SSL_SERVER_CERT_DN subparameter.

Example

net_service_name=
 (DESCRIPTION= 
  (ADDRESS=(PROTOCOL=tcp)(HOST=sales1-svr)(PORT=1521))
  (ADDRESS=(PROTOCOL=tcp)(HOST=sales2-svr)(PORT=1521))
  (CONNECT_DATA=
   (SERVICE_NAME=sales.us.acme.com))
   (SECURITY=
    (SSL_SERVER_CERT_DN="cn=sales,cn=OracleContext,dc=us,dc=acme,dc=com")))

SSL_SERVER_CERT_DN

Purpose

Use the parameter SSL_SEVER_CERT_DN to specify the distinguished name (DN) of the database server. The client uses this information to obtain the list of DNs it expects for each of the servers, enforcing the database server DN to match its service name.

Usage Notes

Use this parameter in conjunction with the sqlnet.ora parameter SSL_SERVER_DN_MATCH to enable server DN matching.

Example

net_service_name= 
 (DESCRIPTION=
   (ADDRESS=...)
   (ADDRESS=...)
   (CONNECT_DATA=
    (SERVICE_NAME=finance.us.acme.com))
   (SECURITY=
    (SSL_SERVER_CERT_DN="cn=finance,cn=OracleContext,dc=us,dc=acme,dc=com")))

7 Local Naming Parameters (tnsnames.ora)

Overview of Local Naming Parameters

General Syntax of tnsnames.ora

Figure 7-1 Basic Format of tnsnames.ora File

Multiple Descriptions in tnsnames.ora

Figure 7-2 Net Service Name with Multiple Connect Descriptors in tnsnames.ora

Multiple Address Lists in tnsnames.ora

Figure 7-3 Multiple Address Lists in tnsnames.ora

Connect-Time Failover and Client Load Balancing with Oracle Connection Managers

Figure 7-4 Multiple Oracle Connection Manager Addresses in tnsnames.ora

Figure 7-5 Client Load Balancing in tnsnames.ora

Local Naming Parameters

Connect Descriptor Descriptions

DESCRIPTION

Purpose

Example

DESCRIPTION_LIST

Purpose

Example

Protocol Address Section

ADDRESS

Purpose

Example

ADDRESS_LIST

Purpose

Example

Optional Parameters for Lists

FAILOVER

Purpose

Default

Values

Example

LOAD_BALANCE

Purpose

Default

Values

Example

SDU

Purpose

Default

Usage

Example

SOURCE_ROUTE

Purpose

Default

Values

Example

TYPE_OF_SERVICE

Purpose

Example

Connect Data Section

CONNECT_DATA

Purpose

Usage Notes

Example

FAILOVER_MODE

Purpose

Subparameters

Example

GLOBAL_NAME

Purpose

Example

HS

Purpose

Default

Values

Example

INSTANCE_NAME

Purpose

Example

RDB_DATABASE

Purpose

Example

SERVER

Purpose

Values

Example

SERVICE_NAME

Purpose

Example

7
Local Naming Parameters (tnsnames.ora)