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Oracle® Database Gateway Installation and Configuration Guide
11g Release 1 (11.1) for AIX 5L Based Systems (64-Bit), HP-UX PA-RISC (64-Bit), HP-UX Itanium, Solaris Operating System (SPARC 64-Bit), Linux x86, and Linux x86-64

B31042-04
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11 Configuring Oracle Database Gateway for ODBC

After installing the gateway and the ODBC driver for the non-Oracle system, perform the following tasks to configure Oracle Database Gateway for ODBC:

  1. Configure the Gateway Initialization Parameter File

  2. Configure Oracle Net for the Gateway

  3. Configure the Oracle Database for Gateway Access

  4. Create Database Links

  5. Encrypt Gateway Initialization Parameter Values

  6. Configure the Gateway to Access Multiple ODBC Data Sources

11.1 Configure the Gateway Initialization Parameter File

Perform the following tasks to configure the gateway initialization file:

  1. Create the Initialization Parameter File

  2. Set the Initialization Parameter Values

11.1.1 Create the Initialization Parameter File

You must create an initialization file for your Oracle Database Gateway for ODBC. Oracle supplies a sample initialization file, initdg4odbc.ora. The sample file is stored in the $ORACLE_HOME/hs/admin directory.

To create an initialization file for the ODBC gateway, copy the sample initialization file and rename it to initsid.ora, where sid is the system identifier (SID) you want to use for the instance of the non-Oracle system to which the gateway connects.

The gateway system identifier (SID) is an alphanumeric character string that identifies a gateway instance. You need one gateway instance, and therefore one gateway SID, for each ODBC source you are accessing.

If you want to access two ODBC sources, you need two gateway SIDs, one for each instance of the gateway. If you have only one ODBC source but want to access it sometimes with one set of gateway parameter settings, and other times with different gateway parameter settings, then you will need multiple gateway SIDs for the single ODBC source. The SID is used as part of the file name for the initialization parameter file.

11.1.2 Set the Initialization Parameter Values

After the initialization file has been created, you must set the initialization parameter values. A number of initialization parameters can be used to modify the gateway behavior. You must set the HS_FDS_CONNECT_INFO and the HS_FDS_SHAREABLE_NAME initialization parameters. Other initialization parameters have defaults or are optional. You can use the default values and omit the optional parameters, or you can specify the parameters with values tailored for your installation. Refer to Appendix C, "Initialization Parameters" for the complete list of initialization parameters that can be set. Changes made to the initialization parameters only take effect in the next gateway session.

The HS_FDS_CONNECT_INFO initialization parameter specifies the information required for connecting to the non-Oracle system. Set the HS_FDS_CONNECT_INFO as follows:

HS_FDS_CONNECT_INFO=dsn_value

where dsn_value is the data source name configured in the odbc.ini file

The HS_FDS_SHAREABLE_NAME initialization parameter specifies the full path of the ODBC driver manager. Set the HS_FDS_SHAREABLE_NAME as follows:

HS_FDS_SHAREABLE_NAME=full_path_of_odbc_driver

where full_path_of_odbc_driver is the full path to the ODBC driver manager

Note:

Before deciding whether to accept the default values or to change them, see Appendix C, "Initialization Parameters" for detailed information about all the initialization parameters.

11.1.2.1 Example: Setting Initialization Parameter Values

The following is an example of an odbc.ini file that uses DataDirect Technologies SQLServer ODBC driver. The ODBC driver is installed in $ODBCHOME, which is the /opt/odbc520 directory.

[ODBC Data Sources]
SQLServerWP=DataDirect 5.20 SQL Server Wire Protocol

[SQLServerWP]
Driver=/opt/odbc520/lib/ivmsss18.so
Description=DataDirect 5.20 SQL Server Wire Protocol
Database=oratst
LogonID=TKHOUSER
Password=TKHOUSER
Address=sqlserver-pc,1433
QuotedId=Yes
AnsiNPW=No

[ODBC]
Trace=0
TraceFile=/opt/odbc520/odbctrace.out
TraceDll=/opt/odbc520/lib/odbctrac.so
InstallDir=/opt/odb520
ConversionTableLocation=/opt/odbc520/tables
UseCursorLib=0

To configure the Gateway for ODBC to use this driver, the following lines are required in initsid.ora:

HS_FDS_CONNECT_INFO=SQLServerWP
HS_FDS_SHAREABLE_NAME=/opt/odbc520/lib/libodbc.so
set ODBCINI=/opt/odbc/odbc.ini

If the ODBC driver you are using requires you to set some environment variables then you can either set them in the initizlization file or in the environment.

The HS_FDS_CONNECT_INFO initialization parameter value must match the ODBC data source name in the odbc.ini file.

Note:

If the ODBC driver supports Quoted Identifiers or Delimited Identifiers it should be turned on.

11.2 Configure Oracle Net for the Gateway

The gateway requires Oracle Net to communicate with the Oracle database. After configuring the gateway, perform the following tasks to configure Oracle Net to work with the gateway:

  1. Configure Oracle Net Listener for the Gateway

  2. Stop and Start the Oracle Net Listener for the Gateway

11.2.1 Configure Oracle Net Listener for the Gateway

The Oracle Net Listener listens for incoming requests from the Oracle database. For the Oracle Net Listener to listen for the gateway, information about the gateway must be added to the Oracle Net Listener configuration file, listener.ora. This file by default is located in $ORACLE_HOME/network/admin, where $ORACLE_HOME is the directory under which the gateway is installed.

The following entries must be added to the listener.ora file:

  • A list of Oracle Net addresses on which the Oracle Net Listener listens

  • The executable name of the gateway that the Oracle Net Listener starts in response to incoming connection requests

A sample of the listener.ora entry (listener.ora.sample) is available in the $ORACLE_HOME/dg4odbc/admin directory where $ORACLE_HOME is the directory under which the gateway is installed.

11.2.1.1 Syntax of listener.ora File Entries

The Oracle database communicates with the gateway using Oracle Net and any supported protocol adapters. The following is the syntax of the address on which the Oracle Net Listener listens using the TCP/IP protocol adapter:

LISTENER=
        (ADDRESS= 
          (PROTOCOL=TCP)
          (HOST=host_name)
          (PORT=port_number))

Where:

Variable Description
host_name is the name of the machine on which the gateway is installed.
port_number specifies the port number used by the Oracle Net Listener. If you have other listeners running on the same machine, then the value of port_number must be different from the other listeners' port numbers.

To direct the Oracle Net Listener to start the gateway in response to incoming connection requests, add an entry to the listener.ora file. The syntax for HP-UX PA-RISC slightly different than the other platforms.

Note:

You must use the same SID value in the tnsnames.ora file and the listener.ora file.

For Linux:

SID_LIST_LISTENER=
   (SID_LIST=
      (SID_DESC= 
         (SID_NAME=gateway_sid)
         (ORACLE_HOME=oracle_home_directory)
         (PROGRAM=dg4odbc)
         (ENVS=LD_LIBRARY_PATH=odbc_library_dir:$ORACLE_HOME/lib)
      )
   )

For HP-UX PA-RISC:

SID_LIST_LISTENER=
   (SID_LIST=
      (SID_DESC= 
         (SID_NAME=gateway_sid)
         (ORACLE_HOME=oracle_home_directory)
         (PROGRAM=dg4odbc)
         (ENVS=SHLIB_PATH=odbc_library_dir:$ORACLE_HOME/lib32)
      )
   )

Where:

Variable Description
gateway_sid specifies the SID of the gateway and matches the gateway SID specified in the connect descriptor entry in the tnsnames.ora file.
oracle_home_directory specifies the Oracle home directory where the gateway resides.
odbc_library_dir specifies the ODBC driver library path
dg4odbc specifies the executable name of the Oracle Database Gateway for ODBC.

If you already have an existing Oracle Net Listener, then add the following syntax to SID_LIST in the existing listener.ora file:

For Linux:

SID_LIST_LISTENER=
(SID_LIST= 
   (SID_DESC=.
     .
   )
   (SID_DESC=.
     .
   )
   (SID_DESC=
      (SID_NAME=gateway_sid)
      (ORACLE_HOME=oracle_home_directory)
      (PROGRAM=dg4odbc)
(ENVS=LD_LIBRARY_PATH=odbc_library_dir:$ORACLE_HOME/lib)
   )
)

For HP-UX PA-RISC:

SID_LIST_LISTENER=
(SID_LIST= 
   (SID_DESC=.
     .
   )
   (SID_DESC=.
     .
   )
   (SID_DESC=
      (SID_NAME=gateway_sid)
      (ORACLE_HOME=oracle_home_directory)
      (PROGRAM=dg4odbc)
      (ENVS=SHLIB_PATH=odbc_library_dir:$ORACLE_HOME/lib32)
   )
)

See Also:

Oracle Net Administrator's Guide for information about changing the listener.ora file.

11.2.2 Stop and Start the Oracle Net Listener for the Gateway

You must stop and restart the Oracle Net Listener to initiate the new settings, as follows:

  1. Set the PATH environment variable to $ORACLE_HOME/bin where $ORACLE_HOME is the directory in which the gateway is installed.

    For example on the Linux platform, if you have the Bourne or Korn Shell, enter the following:

    $ PATH=$ORACLE_HOME/bin:$PATH;export PATH
    $ LD_LIBRARY_PATH=$ORACLE_HOME/lib:$LD_LIBRARY_PATH; export LD_LIBRARY_PATH
    

    If you have the C Shell, enter the following:

    $ setenv PATH $ORACLE_HOME/bin:$PATH
    $ setenv LD_LIBRARY_PATH $ORACLE_HOME/lib:$LD_LIBRARY_PATH
    

    Table 11-1 specifies which parameter value to use for the different platforms:

    Table 11-1 Parameter Values for UNIX Based Platforms

    Platform Parameter Value

    Solaris (SPARC) 64 bit

    LD_LIBRARY_PATH=$ORACLE_HOME/lib

    HP-UX PA-RISC

    SHLIB_PATH=$ORACLE_HOME/lib

    HP-UX Itanium

    LD_LIBRARY_PATH=$ORACLE_HOME/lib

    Linux x86, and Linux x86 64 bit

    LD_LIBRARY_PATH=$ORACLE_HOME/lib

    AIX

    LIBPATH=$ORACLE_HOME/lib


  2. If the listener is already running, use the lsnrctl command to stop the listener and then start it with the new settings, as follows:

    $ lsnrctl stop$ lsnrctl start 
    
  3. Check the status of the listener with the new settings, as follows:

    $ lsnrctl status
    

    The following is a partial output from a lsnrctl status check. In this example dg4odbc is the SID.

.
.
.
Services Summary...
Service "dg4odbc" has 1 instance(s).
  Instance "dg4odbc", status UNKNOWN, has 1 handler(s) for this service...
The command completed successfully

11.3 Configure the Oracle Database for Gateway Access

Before you use the gateway to access an ODBC data source you must configure the Oracle database to enable communication with the gateway over Oracle Net.

To configure the Oracle database you must add connect descriptors to the tnsnames.ora file. By default, this file is in $ORACLE_HOME/network/admin, where $ORACLE_HOME is the directory in which the Oracle database is installed. You cannot use the Oracle Net Assistant or the Oracle Net Easy Config tools to configure the tnsnames.ora file. You must edit the file manually.

A sample of the tnsmanes.ora entry (tnsnames.ora.sample) is available in the $ORACLE_HOME/dg4odbc/admin directory where $ORACLE_HOME is the directory under which the gateway is installed.

See Also:

Oracle Database Administrator's Guide for information about editing the tnsnames.ora file.

11.3.1 Configuring tnsnames.ora

Edit the tnsnames.ora file to add a connect descriptor for the gateway. The following is a syntax of the Oracle Net entry using the TCP/IP protocol:

connect_descriptor=
   (DESCRIPTION=
      (ADDRESS=
         (PROTOCOL=TCP)
         (HOST=host_name)
         (PORT=port_number)
      )
      (CONNECT_DATA=
         (SID=gateway_sid))
      (HS=OK))

Where:

Variable Description
connect_descriptor is the description of the object to connect to as specified when creating the database link, such as dg4odbc.

Check the sqlnet.ora file for the following parameter setting:

names.directory_path = (TNSNAMES)

Note: The sqlnet.ora file is typically stored in $ORACLE_HOME/network/admin.

TCP is the TCP protocol used for TCP/IP connections.
host_name specifies the machine where the gateway is running.
port_number matches the port number used by the Oracle Net Listener that is listening for the gateway. The Oracle Net Listener's port number can be found in the listener.ora file used by the Oracle Net Listener. See "Syntax of listener.ora File Entries".
gateway_sid specifies the SID of the gateway and matches the SID specified in the listener.ora file of the Oracle Net Listener that is listening for the gateway. See "Configure Oracle Net Listener for the Gateway" for more information.
(HS=OK) specifies that this connect descriptor connects to a non-Oracle system.

11.4 Create Database Links

Any Oracle client connected to the Oracle database can access an ODBC data source through the gateway. The Oracle client and the Oracle database can reside on different machines. The gateway accepts connections only from the Oracle database.

A connection to the gateway is established through a database link when it is first used in an Oracle session. In this context, a connection refers to the connection between the Oracle database and the gateway. The connection remains established until the Oracle session ends. Another session or user can access the same database link and get a distinct connection to the gateway and ODBC data source.

Database links are active for the duration of a gateway session. If you want to close a database link during a session, you can do so with the ALTER SESSION statement.

To access the ODBC data source, you must create a database link. A public database link is the most common of database links.

SQL> CREATE PUBLIC DATABASE LINK dblink CONNECT TO
2  "user" IDENTIFIED BY "password" USING 'tns_name_entry';

Where:

Variable Description
dblink is the complete database link name.
tns_name_entry specifies the Oracle Net connect descriptor specified in the tnsnames.ora file that identifies the gateway

After the database link is created you can verify the connection to the ODBC data source, as follows:

SQL> SELECT * FROM DUAL@dblink;

11.5 Encrypt Gateway Initialization Parameter Values

The gateway uses user IDs and passwords to access the information in the remote database. Some user IDs and passwords must be defined in the gateway initialization file to handle functions such as resource recovery. In the current security conscious environment, having plain-text passwords that are accessible in the initialization file is deemed insecure. The dg4pwd encryption utility has been added as part of Heterogeneous Services to help make this more secure. This utility is accessible by this gateway. The initialization parameters which contain sensitive values can be stored in an encrypted form.

See Also:

Oracle Database Heterogeneous Connectivity Administrator's Guide for more information about using this utility.

11.6 Configure the Gateway to Access Multiple ODBC Data Sources

The tasks for configuring the gateway to access multiple ODBC data sources are similar to the tasks for configuring the gateway for a single data source. The configuration example assumes the following:

11.6.1 Multiple ODBC Data Sources Example: Configuring the Gateway

Choose One System ID for Each ODBC Data Source

A separate instance of the gateway is needed for each ODBC data source. Each instance needs its own gateway System ID (SID). For this example, the gateway SIDs are chosen for the instances that access the ODBC data source:

  • dg4odbc2 for the gateway accessing data source dsn2.

  • dg4odbc3 for the gateway accessing data source dsn3.

Create Two Initialization Parameter Files

Create an initialization parameter file for each instance of the gateway by copying the original initialization parameter file $ORACLE_HOME/hs/admin/initdg4odbc.ora, twice, naming one with the gateway SID for dsn2 and the other with the gateway SID for dsn3:

$ cd ORACLE_HOME/hs/admin$ cp initdg4odbc.ora initdg4odbc2.ora$ cp initdg4odbc.ora initdg4odbc3.ora

Change the value of the HS_FDS_CONNECT_INFO parameter in the new files, as follows:

For initdg4odbc2.ora, enter the following:

HS_FDS_CONNECT_INFO=dsn2

For initdg4odbc3.ora, enter the following:

HS_FDS_CONNECT_INFO=dsn3

Note:

If you have multiple gateway SIDs for the same ODBC data source because you want to use different gateway parameter settings at different times, follow the same procedure. You create several initialization parameter files, each with different SIDs and different parameter settings.

11.6.2 Multiple ODBC Data Sources Example: Configuring Oracle Net Listener

Add Entries to listener.ora

Add two new entries to the Oracle Net Listener configuration file, listener.ora. You must have an entry for each gateway instance, even when multiple gateway instances access the same database.

The following example shows the entry for the original installed gateway first, followed by the new entries. The syntax for HP-UX PA-RISC slightly different than the other platforms.

SID_LIST_LISTENER=
(SID_LIST=
   (SID_DESC=
      (SID_NAME=dg4odbc)
      (ORACLE_HOME=oracle_home_directory)
      (PROGRAM=dg4odbc)
(ENVS=LD_LIBRARY_PATH=odbc_library_dir:$ORACLE_HOME/lib)
   )
   (SID_DESC=
      (SID_NAME=dg4odbc2)
      (ORACLE_HOME=oracle_home_directory)
      (PROGRAM=dg4odbc)
(ENVS=LD_LIBRARY_PATH=odbc_library_dir:$ORACLE_HOME/lib)
   )
   (SID_DESC=
      (SID_NAME=dg4odbc3)
      (ORACLE_HOME=oracle_home_directory)
      (PROGRAM=dg4odbc)
(ENVS=LD_LIBRARY_PATH=odbc_library_dir:$ORACLE_HOME/lib)
   )
)

where, oracle_home_directory is the directory where the gateway resides.

11.6.3 Multiple ODBC Data Sources Example: Stopping and Starting the Oracle Net Listener

If the listener is already running, use the lsnrctl command to stop the listener and then start it with the new settings, as follows:

$ lsnrctl stop$ lsnrctl start

11.6.4 Multiple ODBC Data Sources Example: Configuring Oracle Database for Gateway Access

Add two connect descriptor entries to the tnsnames.ora file. You must have an entry for each gateway instance, even if the gateway instances access the same database.

The following example shows the entry for the original installed gateway first, followed by the two entries for the new gateway instances:

old_dsn_using=(DESCRIPTION=
              (ADDRESS=
                (PROTOCOL=TCP)
                (PORT=port_number)
                (HOST=host_name))
                (CONNECT_DATA=
                    (SID=dg4odbc))
               (HS=OK))
new_dsn2_using=(DESCRIPTION=
              (ADDRESS=
                (PROTOCOL=TCP)
                (PORT=port_number)
                (HOST=host_name))
                (CONNECT_DATA=
                    (SID=dg4odbc2))
                (HS=OK))
new_dsn3_using=(DESCRIPTION=
              (ADDRESS=
                (PROTOCOL=TCP)
                (PORT=port_number)
                (HOST=host_name))
                (CONNECT_DATA=
                    (SID=dg4odbc3))
                (HS=OK)) 

The value for PORT is the TCP/IP port number of the Oracle Net Listener that is listening for the gateway. The number can be found in the listener.ora file used by the Oracle Net Listener. The value for HOST is the name of the machine on which the gateway is running. The name also can be found in the listener.ora file used by the Oracle Net Listener.

11.6.5 Multiple ODBC Data Sources Example: Accessing ODBC Data

Enter the following to create a database link for the dg4odbc2 gateway:

SQL> CREATE PUBLIC DATABASE LINK ODBC2 CONNECT TO
  2  "user2" IDENTIFIED BY "password2" USING 'new_dsn2_using';

Enter the following to create a database link for the dg4odbc3 gateway:

SQL> CREATE PUBLIC DATABASE LINK ODBC3 CONNECT TO
  2  "user3" IDENTIFIED BY "password3" USING 'new_dsn3_using';

After the database links are created, you can verify the connection to the new ODBC data sources, as in the following:

SQL> SELECT * FROM ALL_USERS@ODBC2;
SQL> SELECT * FROM ALL_USERS@ODBC3;