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Oracle® Database Gateway Installation and Configuration Guide
11g Release 2 (11.2) for AIX 5L Based Systems (64-Bit), HP-UX Itanium, Solaris Operating System (SPARC 64-Bit), Linux x86, and Linux x86-64

Part Number E12013-04
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5 Configuring Oracle Database Gateway for Informix

After installing the gateway, perform the following tasks to configure Oracle Database Gateway for Informix:

  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. Configure Two-Phase Commit

  6. Encrypt Gateway Initialization Parameter Values

  7. Configure the Gateway to Access Multiple Informix Databases

5.1 Configure the Gateway Initialization Parameter File

Perform the following tasks to configure the gateway initialization parameter file:

  1. Choose a System Identifier for the Gateway

  2. Customize the Initialization Parameter File

5.1.1 Choose a System Identifier for the Gateway

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 Informix database you are accessing. The SID is used as part of the file name for the initialization parameter file. The default SID is dg4ifmx.

You can define a gateway SID, but using the default of dg4ifmx is easier because you do not need to change the initialization parameter file name. However, if you want to access two Informix databases, you need two gateway SIDs, one for each instance of the gateway. If you have only one Informix database and 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 Informix database.

5.1.2 Customize the Initialization Parameter File

The initialization parameter file must be available when the gateway is started. During installation, the following default initialization parameter file is created:

$ORACLE_HOME/dg4ifmx/admin/initdg4ifmx.ora

Where $ORACLE_HOME is the directory under which the gateway is installed.

This initialization file is for the default gateway SID. If you are not using dg4ifmx as the gateway SID, you must rename the initialization parameter file using the SID you chose in the preceding step "Choose a System Identifier for the Gateway" . This default initialization parameter file is sufficient for starting the gateway, verifying a successful installation, and running the demonstration scripts.

A number of initialization parameters can be used to modify the gateway behavior. 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 most important parameter is the HS_FDS_CONNECT_INFO, which describes the connection to the non-Oracle system.

The default initialization parameter file already has an entry for this parameter. The syntax for HS_FDS_CONNECT_INFO is as follows:

HS_FDS_CONNECT_INFO=host_name:port_number/server_name/database_name

Where:

Variable Description
host_name is the host name or IP address of the machine hosting the Informix database.
port_number is the port number of the Informix database server.
server_name specifies the Informix database server name.
database_name is the Informix database name.

This release of gateway can support IPv6. If IPv6 address format is to be specified, you have to wrap it with square brackets to indicate the separation from the port number. For example,

HS_FDS_CONNECT_INFO=[2001:0db8:20C:F1FF:FEC6:38AF]:1300/sr/my_db

See Also:

Appendix C, "Initialization Parameters" and the Oracle Database Heterogeneous Connectivity User's Guide for more information about customizing the initialization parameter file.

5.2 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

5.2.1 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/dg4ifmx/admin directory where $ORACLE_HOME is the directory under which the gateway is installed.

5.2.1.1 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. IPv6 format is supported with this release. Refer to Oracle Database Net Services Reference for detail.
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.

Note:

You must use the same SID value in the listener.ora file and the tnsnames.ora file that will be configured in the next step.

For AIX, Solaris SPARC, and Linux:

SID_LIST_LISTENER=
   (SID_LIST=
      (SID_DESC= 
         (SID_NAME=gateway_sid)
         (ORACLE_HOME=oracle_home_directory)
         (PROGRAM=dg4ifmx)
      )
   )

For HP-UX Itanium:

SID_LIST_LISTENER=
   (SID_LIST=
      (SID_DESC= 
         (SID_NAME=gateway_sid)
         (ORACLE_HOME=oracle_home_directory)
         (ENVS=LD_LIBRARY_PATH=oracle_home_directory/dg4ifmx/driver/lib:oracle_home_directory/lib)
         (PROGRAM=dg4ifmx)
      )
   )

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.
dg4ifmx specifies the executable name of the Oracle Database Gateway for Informix.

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

For AIX, Solaris SPARC, and Linux:

SID_LIST_LISTENER=
(SID_LIST= 
   (SID_DESC=.
     .
   )
   (SID_DESC=.
     .
   )
   (SID_DESC=
      (SID_NAME=gateway_sid)
      (ORACLE_HOME=oracle_home_directory)
      (PROGRAM=dg4ifmx)

   )
)

For HP-UX Itanium:

SID_LIST_LISTENER=
(SID_LIST= 
   (SID_DESC=.
     .
   )
   (SID_DESC=.
     .
   )
   (SID_DESC=
      (SID_NAME=gateway_sid)
      (ORACLE_HOME=oracle_home_directory)
      (ENVS=LD_LIBRARY_PATH=oracle_home_directory/dg4ifmx/driver/lib:oracle_home_directory/lib)
      (PROGRAM=dg4ifmx)
   )
)

See Also:

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

5.2.2 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 5-1 specifies which parameter value to use for the different platforms:

    Table 5-1 Parameter Values for UNIX Based Platforms

    Platform Parameter Value

    Solaris (SPARC) 64 bit

    LD_LIBRARY_PATH_64=$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:

.
.
.
Services Summary...
Service "dg4ifmx" has 1 instance(s).
  Instance "dg4ifmx", status UNKNOWN, has 1 handler(s) for this service...
The command completed successfully

In this example, the service name is dg4ifmx, which is the default SID value assigned during installation.

5.3 Configure the Oracle Database for Gateway Access

Before you use the gateway to access Informix data 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 tnsnames.ora entry (tnsnames.ora.sample) is available in the $ORACLE_HOME/dg4ifmx/admin directory where $ORACLE_HOME is the directory under which the gateway is installed.

5.3.1 Configuring tnsnames.ora

Edit the tnsnames.ora file to add a connect descriptor for the gateway. The following is the 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 dg4ifmx.

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.

See Also:

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

5.4 Create Database Links

Any Oracle client connected to the Oracle database can access Informix data 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 Informix database.

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 Informix server, 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 Informix database, as follows:

SQL> SELECT * FROM DUAL@dblink;

See Also:

Oracle Database Administrator's Guide and Oracle Database Heterogeneous Connectivity User's Guide for more information about using database links.

5.5 Configure Two-Phase Commit

The gateway supports the following transaction capabilities:

The transaction model is set using the HS_TRANSACTION_MODEL initialization parameter. By default, the gateway runs in COMMIT_CONFIRM transaction mode. When the Informix database is updated by a transaction, the gateway becomes the commit point site. The Oracle database commits the unit of work in the Informix database after verifying that all Oracle databases in the transaction have successfully prepared the transaction. Only one gateway instance can participate in an Oracle two-phase commit transaction as the commit point site.

See Also:

Oracle Database Heterogeneous Connectivity User's Guide for information about the two-phase commit process.

To enable the COMMIT_CONFIRM transaction mode, perform the following tasks:

  1. Create a Recovery Account and Password

  2. Create the Transaction Log Table

The log table, called HS_TRANSACTION_LOG, is where two-phase commit transactions are recorded. Alternatively users can specify a different table name by setting a gateway initialization parameter HS_FDS_TRANSACTION_LOG parameter. This table needs to be in the same schema as the recovery account.

5.5.1 Create a Recovery Account and Password

For the gateway to recover distributed transactions, a recovery account and password must be set up in the Informix database. By default, both the user name of the account and the password are RECOVER. The name of the account can be changed with the gateway initialization parameter HS_FDS_RECOVERY_ACCOUNT. The account password can be changed with the gateway initialization parameter HS_FDS_RECOVERY_PWD.

Note:

Oracle recommends that you do not use the default value RECOVER for the user name and password. Moreover, storing plain-text as user name and password in the initialization file is not a good security policy. There is now a utility called dg4pwd that should be used for encryption. Refer to Section 4.2.3, 'Encrypting Initialization parameters' in the Oracle Database Heterogeneous Connectivity User's Guide for further details.
  1. Set up a user account in the Informix database. Both the user name and password must be a valid Informix user name and password.

  2. In the initialization parameter file, set the following gateway initialization parameters:

    • HS_FDS_RECOVERY_ACCOUNT to the user name of the Informix user account you set up for recovery.

    • HS_FDS_RECOVERY_PWD to the password of the Informix user account you set up for recovery.

      See Also:

      Customize the Initialization Parameter File for information about editing the initialization parameter file. For information about HS_FDS_RECOVERY_ACCOUNT and HS_FDS_RECOVERY_PWD, see Appendix C, "Initialization Parameters".

5.5.2 Create the Transaction Log Table

When configuring the gateway for two-phase commit, a table must be created in the Informix database for logging transactions. The gateway uses the transaction log table to check the status of failed transactions that were started at the Informix database by the gateway and registered in the table.

Note:

Updates to the transaction log table cannot be part of an Oracle distributed transaction.

Note:

The information in the transaction log table is required by the recovery process and must not be altered. The table must be used, accessed, or updated only by the gateway.

The table, called HS_TRANSACTION_LOG, consists of two columns, GLOBAL_TRAN_ID, data type CHAR(64) NOT NULL and TRAN_COMMENT, data type CHAR(255).

You can use another name for the log table, other than HS_TRANSACTION_LOG, by specifying the other name using the HS_FDS_TRANSACTION_LOG initialization parameter.

See Also:

Appendix C, "Initialization Parameters" for information about the HS_FDS_TRANSACTION_LOG initialization parameter.

Create the transaction log table in the user account you created in Create a Recovery Account and Password. Because the transaction log table is used to record the status of a gateway transaction, the table must reside at the database where the Informix update takes place. Also, the transaction log table must be created under the owner of the recovery account.

Note:

To utilize the transaction log table, users of the gateway must be granted privileges on the table.

To create a transaction log table use the dg4ifmx_tx.sql script, located in the directory $ORACLE_HOME/dg4ifmx/admin where $ORACLE_HOME is the directory under which the gateway is installed, as follows:

  1. Login as user ID RECOVER.

  2. Set environment variable DELIMIDENT.

    If you have the Bourne or Korn Shell, enter the following:

    $ DELIMIDENT = y; export DELIMIDENT
    

    If you have the C Shell, enter the following:

    $ setenv DELIMIDENT y
    
  3. Execute the script using dbaccess, as follows.

    $ cd $ORACLE_HOME/dg4ifmx/admin
    $ dbaccess database_name dg4ifmx_tx.sql
    

5.6 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 that contain sensitive values can be stored in an encrypted form.

See Also:

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

5.7 Configure the Gateway to Access Multiple Informix Databases

The tasks for configuring the gateway to access multiple Informix databases are similar to the tasks for configuring the gateway for a single database. The configuration example assumes the following:

5.7.1 Multiple Informix Databases Example: Configuring the Gateway

Choose One System ID for Each Informix Database

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

  • dg4ifmx2 for the gateway accessing database db2.

  • dg4ifmx3 for the gateway accessing database db3.

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/dg4ifmx/admin/initdg4ifmx.ora, twice, naming one with the gateway SID for db2 and the other with the gateway SID for db3:

$ cd $ORACLE_HOME/dg4ifmx/admin
$ cp initdg4ifmx.ora initdg4ifmx2.ora
$ cp initdg4ifmx.ora initdg4ifmx3.ora

Change the value of the HS_FDS_CONNECT_INFO parameter in the new files.

For initdg4ifmx2.ora, enter the following:

HS_FDS_CONNECT_INFO=204.179.79.15:3900/sr2/db2

For initdg4ifmx3.ora, enter the following:

HS_FDS_CONNECT_INFO=204.179.79.15:3900/sr3/db3

Note:

If you have multiple gateway SIDs for the same Informix database 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.

5.7.2 Multiple Informix Databases 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.

SID_LIST_LISTENER=
(SID_LIST=
   (SID_DESC=
      (SID_NAME=dg4ifmx)
      (ORACLE_HOME=oracle_home_directory)
      (PROGRAM=dg4ifmx)
   )
   (SID_DESC=
      (SID_NAME=dg4ifmx2)
      (ORACLE_HOME=oracle_home_directory)
      (PROGRAM=dg4ifmx)
   )
   (SID_DESC=
      (SID_NAME=dg4ifmx3)
      (ORACLE_HOME=oracle_home_directory)
      (PROGRAM=dg4ifmx)
   )
)

where, oracle_home_directory is the directory where the gateway resides.

5.7.3 Multiple Informix Databases 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

5.7.4 Multiple Informix Databases Example: Configuring Oracle Database for Gateway Access

5.7.4.1 Configuring Oracle Net for Multiple Gateway Instances

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

old_db_using=(DESCRIPTION=
              (ADDRESS=
                (PROTOCOL=TCP)
                (PORT=port_number)
                (HOST=host_name))
                (CONNECT_DATA=
                    (SID=dg4ifmx))
               (HS=OK))
new_db2_using=(DESCRIPTION=
              (ADDRESS=
                (PROTOCOL=TCP)
                (PORT=port_number)
                (HOST=host_name))
                (CONNECT_DATA=
                    (SID=dg4ifmx2))
                (HS=OK))
new_db3_using=(DESCRIPTION=
              (ADDRESS=
                (PROTOCOL=TCP)
                (PORT=port_number)
                (HOST=host_name))
                (CONNECT_DATA=
                    (SID=dg4ifmx3))
                (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.

5.7.5 Multiple Informix Databases Example: Accessing Informix Data

Enter the following to create a database link for the dg4ifmx2 gateway:

SQL> CREATE PUBLIC DATABASE LINK IFMX2 CONNECT TO
  2  "user2" IDENTIFIED BY "password2" USING 'new_db2_using';

Enter the following to create a database link for the dg4ifmx3 gateway:

SQL> CREATE PUBLIC DATABASE LINK IFMX3 CONNECT TO
  2  "user3" IDENTIFIED BY "password3" USING 'new_db3_using';

After the database links are created, you can verify the connection to the new Informix databases, as in the following:

SQL> SELECT * FROM ALL_USERS@IFMX2;
SQL> SELECT * FROM ALL_USERS@IFMX3;