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6 Local Naming Parameters (tnsnames.ora)
This chapter provides a complete listing of the
tnsnames.ora
file configuration parameters.
This chapter contains the following topics:
Overview of Local Naming Parameters
General Syntax of tnsnames.ora
Multiple Descriptions in tnsnames.ora
Multiple Address Lists in tnsnames.ora
Connect-Time Failover and Client Load Balancing with Oracle Connection Managers
Connect Descriptor Descriptions
Optional Parameters for Address Lists
Overview of Local Naming Parameters
This
tnsnames.ora
file is a configuration file that contains
net 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. 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 files. For example, the order checking the
tnsnames.ora
file is as follows:
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.
If the
TNS_ADMIN
environment variable is not set, then Oracle Net will check 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 operating system-specific documentationGeneral Syntax of tnsnames.ora
The basic syntax for a
tnsnames.ora
file is shown in
Example 6-1
.
Example 6-1 Basic Format of tnsnames.ora File
net_service_name= (DESCRIPTION= (ADDRESS=( protocol_address_information )) (CONNECT_DATA= (SERVICE_NAME= service_name )))
In the preceding example,
DESCRIPTION
contains the connect descriptor,
ADDRESS
contains the protocol address, and
CONNECT_DATA
contains the database service identification information.
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
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))))Note:
Oracle Net Manager does not support the creation of multiple connect descriptors for a net service name when using Oracle Connection Manager.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 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 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
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:
Oracle Net Manager supports only the creation of one protocol address list for a connect descriptor.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
sample1= (DESCRIPTION= (SOURCE_ROUTE=yes) (ADDRESS=(PROTOCOL=tcp)(HOST=host1)(PORT=1630)) # 1 (ADDRESS_LIST= (FAILOVER=on) (LOAD_BALANCE=off) # 2 (ADDRESS=(PROTOCOL=tcp)(HOST=host2a)(PORT=1630)) (ADDRESS=(PROTOCOL=tcp)(HOST=host2b)(PORT=1630))) (ADDRESS=(PROTOCOL=tcp)(HOST=host3)(PORT=1521)) # 3 (CONNECT_DATA=(SERVICE_NAME=Sales.us.example.com)))In Example 6-4 , the syntax does the following:
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 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 connects to the database service using the following protocol address:
(ADDRESS=(PROTOCOL=tcp)(HOST=host3)(PORT=1521))Example 6-5 illustrates client load balancing among two Oracle Connection Managers and two protocol addresses:
Example 6-5 Client Load Balancing in tnsnames.ora
sample2= (DESCRIPTION= (LOAD_BALANCE=on) # 1 (FAILOVER=on) (ADDRESS_LIST= (SOURCE_ROUTE=yes) (ADDRESS=(PROTOCOL=tcp)(HOST=host1)(PORT=1630)) # 2 (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.example.com))) # 3In Example 6-5 , the syntax does the following:
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
.
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.
DESCRIPTION
To specify a container for a connect descriptor. Put this parameter under the
DESCRIPTION_LIST
parameter.
DESCRIPTION_LIST
To define a list of connect descriptors for a particular net service name.
net_service_name = (DESCRIPTION_LIST= (DESCRIPTION= (ADDRESS=...) (CONNECT_DATA=(SERVICE_NAME=sales.example.com))) (DESCRIPTION= (ADDRESS=...) (CONNECT_DATA=(SERVICE_NAME=sales2.us.example.com))))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.
ADDRESS
To define a single listener protocol address. Put this parameter under either the
ADDRESS_LIST
parameter or the
DESCRIPTION
parameter.
See Also:
Chapter 4, "Protocol Address Configuration" for descriptions of the correct parameters to use for each protocolADDRESS_LIST
To define a list of protocol addresses. 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.
Optional Parameters for Address Lists
For multiple addresses, the following parameters are available:
ENABLE
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. The keepalive feature allows the caller to detect a terminated remote server, although typically it takes 2 hours or more to notice. 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.
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.
Put this parameter under 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.
on
for
DESCRIPTION_LIST
,
DESCRIPTION
, and
ADDRESS_LIST
.
yes
|
on
|
true
no
|
off
|
false
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 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 first address in the address list. If the connection fails and the failover parameter is enabled, then Oracle Net tries the addresses sequentially until one succeeds.
Put this parameter under either the
DESCRIPTION_LIST
parameter, the
DESCRIPTION
parameter, or the
ADDRESS_LIST
parameter.
on for
DESCRIPTION_LIST
yes
|
on
|
true
no
|
off
|
false
RECV_BUF_SIZE
To specify, in bytes, the buffer space for receive operations of sessions. 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.
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.
Setting this parameter in the connect descriptor for a client overrides the
RECV_BUF_SIZE
parameter at the client-side
sqlnet.ora
file.
See Also:
Oracle Database Net Services Administrator's Guide for additional information about configuring this parameterTo instruct Oracle Net to optimize the transfer rate of data packets being sent across the network with a specified session data unit (SDU) size.
Put this parameter under the
DESCRIPTION
parameter.
8192 bytes (8 KB).
512 to 65535 bytes.
Setting this parameter in the connect descriptor for a client overrides the
DEFAULT_SDU_SIZE
parameter at client-side
sqlnet.ora
file.
See Also:
Oracle Database Net Services Administrator's Guide for complete SDU usage and configuration informationSEND_BUF_SIZE
To specify, in bytes, the buffer space for send operations of sessions. This parameter is supported by the TCP/IP, TCP/IP with SSL, and SDP protocols.
Note:
Additional protocols might support this parameter on certain operating systems. Refer to the operating system-specific documentation for additional information about additional protocols.
Put this parameter under the
DESCRIPTION
parameter or at the end of the protocol address.
The default value for this parameter is operating system-specific.
Setting this parameter in the connect descriptor for a client overrides the
SEND_BUF_SIZE
parameter at the client-side
sqlnet.ora
file.
See Also:
Oracle Database Net Services Administrator's Guide for additional information about configuring this parameterTo 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.
Put this parameter under either the
DESCRIPTION_LIST
parameter, the
DESCRIPTION
parameter, or the
ADDRESS_LIST
parameter.
yes
|
on
no
|
off
See Also:
Oracle Database Net Services Administrator's Guide for complete configuration informationTYPE_OF_SERVICE
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.
Put this parameter under the
DESCRIPTION
parameter.
Connection Data Section
The connection data section of the
tnsnames.or
a file specifies the name of the destination service. The following parameters are available:
To define the service to which to connect, such as
SERVICE_NAME
.
Put this parameter under the
DESCRIPTION
parameter.
CONNECT_DATA
permits the following additional parameters:
FAILOVER_MODE
To instruct Oracle Net to fail over to a different listener if the first listener fails during run time. 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.
Put this parameter under the
CONNECT_DATA
parameter.
FAILOVER_MODE
supports the following parameters:
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. 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.
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, then
RETRIES
defaults to five retry attempts.
DELAY
: Specify 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 informationTo identify the Oracle Rdb database.
Put this parameter under the
CONNECT_DATA
parameter.
To direct Oracle Net to connect to a non-Oracle system through Heterogeneous Services .
Put this parameter under the
CONNECT_DATA
parameter.
See Also:
Oracle Database Net Services Administrator's Guide for complete configuration informationINSTANCE_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.
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
To specify the file name of an Oracle Rdb database.
Put this parameter under the
CONNECT_DATA
parameter.
SERVER
To direct the listener to connect the client to a specific type of service handler .
Put this parameter under the
CONNECT_DATA
parameter.
dedicated
to specify whether client requests be served by
dedicated server
shared
to specify whether client request be served by
shared server
pooled
to get a connection from the connection pool if
database resident connection pooling is enabled on the server
Notes:
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.
See Also:
Oracle Database Net Services Administrator's Guide for additional information about database resident connection pooling
Oracle Call Interface Programmer's Guide and Oracle Database Administrator's Guide for additional information about enabling and configuring database resident connection pooling
SERVICE_NAME
To identify the Oracle Database database service to access. 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
Security Section
The security section of the
tnsnames.or
a file specifies the following security-related parameters for use with Oracle Advanced Security features:
SECURITY
To enable secure connections. Put this parameter under the
DESCRIPTION
parameter.
SECURITY
permits the
SSL_SERVER_CERT_DN
parameter.
SSL_SERVER_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.
Use this parameter with the
sqlnet.ora
parameter
SSL_SERVER_DN_MATCH
to enable server DN matching.
See Also:
Oracle Database Security GuideTimeout Parameters
The timeout section of the
tnsnames.or
a file provides the ability to specify timeout and retry configuration through the TNS connect string. The following parameters can now be set at the
DESCRIPTION
level of a connect string:
CONNECT_TIMEOUT
To specify the timeout duration in seconds for a client to establish an Oracle Net connection to an Oracle database. 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.
The default value of
CONNECT_TIMEOUT
is dependent on the
TCP_CONNECT_TIMEOUT
parameter. Oracle recommends setting the
CONNECT_TIMEOUT
value slightly greater than the
TCP_CONNECT_TIMEOUT
value.
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.
RETRY_COUNT
To specify the number of times an
ADDRESS
list is traversed before the connection attempt is terminated. The default value is 0.
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.
RETRY_COUNT
is only supported at
DESCRIPTION
level in connect string.
When using SCAN listeners in an Oracle Real Application Clusters environment, with
FAILOVER = on
, setting the
RETRY_COUNT
parameter to
2
means the three SCAN IP addresses are traversed three times each, such that there are nine connect attempts (3 * 3).
TRANSPORT_CONNECT_TIMEOUT
To specify the transportation timeout duration in seconds for a client to establish an Oracle Net connection to an Oracle Database.
This parameter is put under the
DESCRIPTION
parameter.
The
TRANSPORT_CONNECT_TIMEOUT
parameter specifies the time, in seconds, for a client to establish a TCP connection to the database server. The default value is 60 seconds.
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.
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