The tnsnames.ora file is a configuration file that contains network service name s mapped to connect descriptor s 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.

• Tnsnames Ora File Location

This chapter provides a complete listing of the tnsnames.ora file configuration parameters. This chapter contains the following topics:

6.1 Overview of Local Naming Parameters

The tnsnames.ora file is a configuration file that contains network 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, the tnsnames.ora file is located in the ORACLE_HOME/network/admin directory. Oracle Net will check the other directories for the configuration file. For example, the order checking the tnsnames.ora file is as follows:

1. The directory specified by the TNS_ADMIN environment variable. If the file is not found in the directory specified, then it is assumed that the file does not exist.

2. If the TNS_ADMIN environment variable is not set, then Oracle Net checks the ORACLE_HOME/network/admin directory.

Note:

On Microsoft Windows, the TNS_ADMIN environment variable is used if it is set in the environment of the process. If the TNS_ADMIN environment variable is not defined in the environment, or the process is a service which does not have an environment, then Microsoft Windows scans the registry for a TNS_ADMIN parameter.

See Also:

• Oracle Database Global Data Services Concepts and Administration Guide for information about management of global services

• Oracle operating system-specific documentation

6.2 General Syntax of tnsnames.ora

The basic syntax for a tnsnames.ora file is shown in Example 6-1.

In the preceding example, DESCRIPTION contains the connect descriptor, ADDRESS contains the protocol address, and CONNECT_DATA contains the database service identification information.

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6.3 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. Example 6-2 shows two connect descriptors with multiple addresses. DESCRIPTION_LIST defines a list of connect descriptors.

Example 6-2 Net Service Name with Multiple Connect Descriptors in tnsnames.ora

Note:

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

6.4 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 Example 6-3, two address lists are presented. The first address list features client load balancing and no connect-time failover, affecting only those protocol addresses within its ADDRESS_LIST. The second protocol address list features no client load loading balancing, but does have connect-time failover, affecting only those protocol addresses within its ADDRESS_LIST. The client first tries the first or second protocol address at random, then tries protocol addresses three and four sequentially.

Example 6-3 Multiple Address Lists in tnsnames.ora

Note:

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

• Oracle Net Services supports the IFILE parameter in the tnsnames.ora file, with up to three levels of nesting. The parameter is added manually to the file. The following is an example of the syntax:

  Refer to Oracle Database Reference for additional information.

6.5 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.

Example 6-4 illustrates failover of multiple Oracle Connection Manager protocol addresses.

Example 6-4 Multiple Oracle Connection Manager Addresses in tnsnames.ora

In Example 6-4, the syntax does the following:

1. The client is instructed to connect to the protocol address of the first Oracle Connection Manager, as indicated by:

2. The first Oracle Connection Manager is 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:

3. Oracle Connection Manager connects to the database service using the following protocol address:

Example 6-5 illustrates client load balancing among two Oracle Connection Managers and two protocol addresses:

In Example 6-5, the syntax does the following:

1. The client is instructed to pick an ADDRESS_LIST at random and to fail over to the other if the chosen ADDRESS_LIST fails. This is indicated by the LOAD_BALANCE and FAILOVER parameters being set to on.

2. When an ADDRESS_LIST is chosen, the client first connects to Oracle Connection Manager, using the Oracle Connection Manager protocol address that uses port 1630 indicated for the ADDRESS_LIST.

3. Oracle Connection Manager then connects to the database service, using the protocol address indicated for the ADDRESS_LIST.

6.6 Connect Descriptor Descriptions

Each connect descriptor is contained within the DESCRIPTION parameter. Multiple connect descriptors are characterized by the DESCRIPTION_LIST parameter. These parameters are described in this section.

6.6.1 DESCRIPTION

To specify a container for a connect descriptor.

Usage Notes

When using more than one DESCRIPTION parameter, put the parameters under the DESCRIPTION_LIST parameter.

6.6.2 DESCRIPTION_LIST

To define a list of connect descriptors for a particular net service name.

Example

6.7 Protocol Address Section

The protocol address section of the tnsnames.ora file specifies the protocol addresses of the listener. If there is only one listener protocol address, then use the ADDRESS parameter. If there is more than one address, then use the ADDRESS_LIST parameter.

6.7.1 ADDRESS

To define a single listener protocol address.

Usage Notes

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

See Also:

Protocol Address Configuration for descriptions of the correct parameters to use for each protocol

6.7.1.1 HTTPS_PROXY

Purpose

To specify HTTP proxy host name for tunneling SSL client connections.

Usage Notes

The clients can tunnel secure connections over forward HTTP proxy using HTTP CONNECT method. This helps in accessing the public cloud database service as it eliminates the requirement to open an outbound port on a client side firewall. This parameter is applicable only to the connect descriptors where PROTOCOL=TCPS. This is similar to the web browser setting for intranet users who want to connect to internet hosts. Increase the forward web proxy read timeout for requests to a higher value depending on client queries. Otherwise, the forward web proxy closes the connection assuming that no requests are made from the client.

Successful connection depends on specific proxy configurations. The performance of data transfers depends on proxy capacity. Oracle recommends not to use this feature in production environments where performance is critical.

Configuring tnsnames.ora for the HTTP proxy may not be enough depending your organization’s network configuration and security policies. For example, some networks require a username and password for the HTTP proxy.

Oracle Client versions earlier than 18c does not support connections through HTTP proxy.

Contact your network administrator to open outbound connections to hosts in the oraclecloud.com domain using the relevant port, without going through an HTTP proxy. For example, port 1522.

Values

HTTP proxy host name that can make an outbound connection to the internet hosts.

6.7.1.2 HTTPS_PROXY_PORT

Purpose

To specify forward HTTP proxy host port for tunneling SSL client connections.

Usage Notes

It forwards the HTTP proxy host port that receives HTTP CONNECT method. This parameter should be used along with HTTPS_PROXY_PORT. This value takes effect only when SQLNET.USE_HTTPS_PROXY=1 is set in sqlnet.ora.

Values

port number

6.7.2 ADDRESS_LIST

To define a list of protocol addresses.

Usage Notes

If there is only one listener protocol address, then ADDRESS_LIST is not necessary.

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

6.8 Optional Parameters for Address Lists

For multiple addresses, the following parameters are available:

6.8.1 ENABLE

To allow the caller to detect a terminated remote server, typically it takes 2 hours or more to notice.

Usage Notes

The keepalive feature on the supported TCP transports can be enabled for a net service client by putting (ENABLE=broken) under the DESCRIPTION parameter in the connect string. On the client side, the default for tcp_keepalive is off. Operating system TCP configurables, which vary by platform, define the actual keepalive timing details.

Example

Although the preceding example has multiple addresses, the ADDRESS_LIST parameter was not used. This is because the ADDRESS_LIST parameter is not mandatory.

6.8.2 FAILOVER

To enable or disable connect-time failover for multiple protocol addresses.

Usage Notes

When you set the parameter to on, yes, or true, Oracle Net fails over at connect time 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.

Put this parameter under the DESCRIPTION_LIST parameter, the DESCRIPTION parameter, or the ADDRESS_LIST parameter.

Note:

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.

on for the DESCRIPTION_LIST, DESCRIPTION, and ADDRESS_LIST parameters

Values

• yesontrue

• noofffalse

6.8.3 LOAD_BALANCE

To enable or disable client load balancing for multiple protocol addresses.

Usage Notes

When you set the parameter to on, yes, or true, Oracle Net goes 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.

Put this parameter under the DESCRIPTION_LIST parameter, the DESCRIPTION parameter, or the ADDRESS_LIST parameter.

on for DESCRIPTION_LIST

Values

• yesontrue

• noofffalse

6.8.4 RECV_BUF_SIZE

To specify, in bytes, the buffer space for receive operations of sessions.

Usage Notes

This parameter is supported by the TCP/IP, TCP/IP with SSL, and SDP protocols.

Put this parameter under the DESCRIPTION parameter or at the end of the protocol address.

Setting this parameter in the connect descriptor for a client overrides the RECV_BUF_SIZE parameter at the client-side sqlnet.ora file.

Note:

Additional protocols might support this parameter on certain operating systems. Refer to the operating system-specific documentation for additional information about additional protocols.

The default value for this parameter is specific to the operating system. The default for the Linux 2.6 operating system is 87380 bytes.

Example

See Also:

Oracle Database Net Services Administrator's Guide for additional information about configuring this parameter

6.8.5 SDU

To instruct Oracle Net to optimize the transfer rate of data packets being sent across the network with a specified session data unit (SDU) size.

Usage Notes

Put this parameter under the DESCRIPTION parameter.

Setting this parameter in the connect descriptor for a client overrides the DEFAULT_SDU_SIZE parameter at client-side sqlnet.ora file.

8192 bytes (8 KB)

Values

512 to 2097152 bytes.

See Also:

Oracle Database Net Services Administrator's Guide for complete SDU usage and configuration information

6.8.6 SEND_BUF_SIZE

To specify, in bytes, the buffer space for send operations of sessions.

Usage Notes

This parameter is supported by the TCP/IP, TCP/IP with SSL, and SDP protocols.

Put this parameter under the DESCRIPTION parameter or at the end of the protocol address.

Setting this parameter in the connect descriptor for a client overrides the SEND_BUF_SIZE parameter at the client-side sqlnet.ora file.

Note:

Additional protocols might support this parameter on certain operating systems. Refer to the operating system-specific documentation for information about additional protocols.

The default value for this parameter is operating system specific. The default for the Linux 2.6 operating system is 16 KB.

Example

See Also:

Oracle Database Net Services Administrator's Guide for additional information about configuring this parameter

6.8.7 SOURCE_ROUTE

To enable routing through multiple protocol addresses.

Usage Notes

When you set this parameter 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.

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

off

Values

• yeson

• nooff

See Also:

Oracle Database Net Services Administrator's Guide for complete configuration information

6.8.8 TYPE_OF_SERVICE

To specify the type of service to use for an Oracle Rdb database.

Usage Notes

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.

Put this parameter under the DESCRIPTION parameter.

6.9 Connection Data Section

The connection data section of the tnsnames.ora file specifies the name of the destination service. The following parameters are available:

6.9.1 CONNECT_DATA

To define the service to which to connect, such as SERVICE_NAME.

Usage Notes

Put this parameter under the DESCRIPTION parameter.

CONNECT_DATA permits the following additional parameters:

6.9.1.1 SHARDING_KEY

Purpose

To route the database request to a particular shard.

Usage Notes

Put this parameter under the CONNECT_DATA parameter.

Example

See Also:

Oracle Database Net Services Administrator's Guide for additional information about the use of the SHARDING_KEY parameter

6.9.1.2 SUPER_SHARDING_KEY

Purpose

To route the database request to a collection of shards.

Usage Notes

Put this parameter under the CONNECT_DATA parameter.

Example

See Also:

Oracle Database Net Services Administrator's Guide for additional information about the use of the SUPER_SHARDING_KEY parameter

6.9.2 FAILOVER_MODE

To instruct Oracle Net to fail over to a different listener if the first listener fails during run time.

Usage Notes

Depending upon the configuration, the 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.

Put this parameter under the CONNECT_DATA parameter.

FAILOVER_MODE supports the following parameters:

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

• TYPE: Specifies 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. For example, if a user's connection is lost, then 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 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: Specifies 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.

• TRANSACTION: Allows the database to complete the current database transaction following a recoverable error. This parameter is used with the COMMIT_OUTCOME=TRUE parameter.

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

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

Note:

If a callback function is registered, then RETRIES and DELAY parameters are ignored.

See Also:

Oracle Database Net Services Administrator's Guide for additional configuration information

6.9.3 GLOBAL_NAME

To identify the Oracle Rdb database.

Usage Notes

Put this parameter under the CONNECT_DATA parameter.

6.9.4 HS

To direct Oracle Net to connect to a non-Oracle system through Heterogeneous Services.

Usage Notes

Put this parameter under the CONNECT_DATA parameter.

None

Values

See Also:

Oracle Database Net Services Administrator's Guide for complete configuration information

6.9.5 INSTANCE_NAME

To identify the database instance to access.

Usage Notes

Set the value to the value specified by the INSTANCE_NAME parameter in the initialization parameter file.

Put this parameter under the CONNECT_DATA parameter.

See Also:

Oracle Database Net Services Administrator's Guide for additional information about the use of INSTANCE_NAME

6.9.6 RDB_DATABASE

To specify the file name of an Oracle Rdb database.

Usage Notes

Put this parameter under the CONNECT_DATA parameter.

6.9.7 SERVER

To direct the listener to connect the client to a specific type of service handler.

Usage Notes

Put this parameter under the CONNECT_DATA parameter.

• dedicated to specify whether client requests be served by dedicated server.

• shared to specify whether client requests be served by a dispatcher or shared server.

• pooled to get a connection from the connection pool if database resident connection pooling is enabled on the 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.

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

6.9.8 SERVICE_NAME

To identify the Oracle Database database service to access.

Usage Notes

Set the value to a value specified by the SERVICE_NAMES parameter in the initialization parameter file.

Put this parameter under the CONNECT_DATA parameter.

See Also:

Oracle Database Net Services Administrator's Guide for additional information about the use of the SERVICE_NAME parameter

6.10 Security Section

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

6.10.1 SECURITY

To change the security properties of the connection. Put this parameter under the DESCRIPTION parameter.

Usage Notes

The parameters permitted under SECURITY are SSL_SERVER_CERT_DN and AUTHENTICATION_SERVICE.

6.10.2 SSL_SERVER_CERT_DN

To specify the distinguished name (DN) of the database server.

Usage Notes

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.

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

See Also:

6.11 Timeout Parameters

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The timeout section of the tnsnames.ora file provides the ability to specify timeout and retry configuration through the TNS connect string. The following parameters can be set at the DESCRIPTION level of a connect string:

6.11.1 CONNECT_TIMEOUT

To specify the timeout duration in ms, sec, or min for a client to establish an Oracle Net connection to an Oracle database.

Usage Notes

Put this parameter under the DESCRIPTION parameter.

The timeout interval specified by CONNECT_TIMEOUT is a superset of the TCP connect timeout interval. It includes the time to be connected to the database instance providing the requested service, not just the duration of the TCP connection. It accepts different timeouts with or without space between the value and the unit. In case, no unit is mentioned, the default unit is sec.

The timeout interval is applicable for each ADDRESS in an ADDRESS_LIST, and each IP address to which a host name is mapped.

The CONNECT_TIMEOUT parameter is equivalent to the sqlnet.ora parameter SQLNET.OUTBOUND_CONNECT_TIMEOUT, and overrides it.

6.11.2 RETRY_COUNT

To specify the number of times an ADDRESS list is traversed before the connection attempt is terminated.

Usage Notes

Put this parameter under the DESCRIPTION parameter.

When a DESCRIPTION_LIST is specified, each DESCRIPTION is traversed multiple times based on the specified number of retries.

6.11.3 RETRY_DELAY

To specify the delay in seconds between subsequent retries for a connection. This parameter works in conjunction with RETRY_COUNT parameter.

Usage Notes

Put this parameter under the DESCRIPTION parameter.

When a DESCRIPTION_LIST is specified, each DESCRIPTION is traversed multiple times based on the specified number of retries, and the specific delay for the description.

Tnsnames Ora File Location

6.11.4 TRANSPORT_CONNECT_TIMEOUT

To specify the transport connect timeout duration in ms, sec, or min for a client to establish an Oracle Net connection to an Oracle database.

Usage Notes

This parameter is put under the DESCRIPTION parameter.

The TRANSPORT_CONNECT_TIMEOUT parameter specifies the time, in ms, sec, or min, for a client to establish a TCP connection to the database server. It accepts different timeouts with or without space between the value and the unit. The default value is 60 seconds. In case, no unit is mentioned, the default unit is sec.

The timeout interval is applicable for each ADDRESS in an ADDRESS_LIST description, and each IP address that a host name is mapped. The TRANSPORT_CONNECT_TIMEOUT parameter is equivalent to the sqlnet.ora parameter TCP.CONNECT_TIMEOUT, and overrides it.

6.12 Compression Parameters

The compression section of the tnsnames.ora file provides the ability to enable compression and specify compression levels. The following parameters can be set at the DESCRIPTION level of a connect string:

6.12.1 COMPRESSION

To enable or disable data compression.

Usage Notes

Put this parameter under the DESCRIPTION parameter.

Setting this parameter in the connect descriptor for a client overrides the SQLNET.COMPRESSION parameter in the client-side sqlnet.ora file.

off

Values

• on to enable data compression.

• off to disable data compression.

6.12.2 COMPRESSION_LEVELS

To specify the compression level.

Usage Notes

The compression levels are used at the time of negotiation to verify which levels are used at both ends, and select one level. Put this parameter under the DESCRIPTION parameter.

This parameter is used with the COMPRESSION parameter. Setting this parameter in the connect descriptor for a client overrides the SQLNET.COMPRESSION_LEVELS parameter in the client-side sqlnet.ora file.

low

Values

• low for low CPU usage and a low compression ratio.

• high for high CPU usage and a high compression ratio.