2 Configuring the Gateway

2.1.1 Task 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 Microsoft SQL Server database you are accessing. The SID is used as part of the file name for the initialization parameter file. The default SID is tg4msql.

You can define a gateway SID, but using the default of tg4msql is easier because you do not need to change the initialization parameter file name. However, if you want to access two Microsoft SQL Server databases, you need two gateway SIDs, one for each instance of the gateway. If you have one Microsoft SQL Server database and want to access it sometimes with one set of gateway parameter settings, and other times with different gateway parameter settings, you can do that by having multiple gateway SIDs for the single Microsoft SQL Server database.

2.1.2 Task 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\tg4msql\admin\inittg4msql.ora

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

If you are not using tg4msql as the gateway SID, you must rename the initialization parameter file using the SID you chose in Task 1. This default initialization parameter file is sufficient for starting the gateway, verifying a successful installation, and running the demonstration scripts.

In the initialization parameter file, specify the Microsoft SQL Server connection as follows:

HS_FDS_CONNECT_INFO=server_name.database_name

If you specify only .database_name, omitting server_name (but including the period), the gateway uses the following subtree of the Microsoft Windows registry to determine server_name:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSSQLServer\Client\ConnectTo

A number of initialization parameters can be used to modify gateway behavior. You might want to change the initialization parameter file later to meet system requirements.

2.2.1 Task 1: Configure Oracle Net Services TNS Listener for the Gateway

Oracle Net Services uses the TNS listener to receive incoming connections from a Oracle Net Services client. The TNS listener and the gateway must reside on the same machine.

The TNS listener listens for incoming requests from the Oracle database server. For the TNS listener to listen for the gateway, information about the gateway must be added to the TNS listener configuration file, listener.ora. This file 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 Services addresses on which the TNS listener listens

• The gateway that the TNS listener starts in response to incoming connection requests

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

SID_LIST_LISTENER=
   (SID_LIST=
      (SID_DESC= 
         (SID_NAME=gateway_sid)
         (ORACLE_HOME=oracle_home_directory)
         (PROGRAM=tg4msql)
      )
   )

SID_LIST_LISTENER=
(SID_LIST= 
   (SID_DESC=.
     .
   )
   (SID_DESC=.
     .
   )
   (SID_DESC=
      (SID_NAME=gateway_sid)
      (ORACLE_HOME=oracle_home_directory)
      (PROGRAM=tg4msql)
   )
)

2.2.2 Task 2: Stop and Start the TNS Listener for the Gateway

The TNS listener must be started to initiate the new settings, as follows:

1. Select Services from the Windows Control Panel. (For example, for Windows 2000, from the Windows Start menu select Settings, Control Panel, Administrative Tools, and then select Services).

2. Select the TNSListener service for the gateway.

3. If the service is already running, click Stop to stop it.

4. Click Start to start or restart the service.

2.3.1 Configuring Oracle Net Services for the Oracle Database Server

To configure the server you add connect descriptors to the tnsnames.ora file. You cannot use the Oracle Net Services Assistant or the Oracle Net Services Easy Config tools to configure the tnsnames.ora file. You must edit the file manually.

For the Oracle database server to access the gateway, it needs a service name entry or a connect descriptor name entry in the tnsnames.ora file to tell the Oracle database server where to make connections. By default, this file is in ORACLE_HOME\network\admin, where ORACLE_HOME is the directory in which the Oracle database server is installed. The tnsnames.ora file is required by the Oracle database server accessing the gateway, but not by the gateway.

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

2.6.1 Multiple Databases Example: Configuring the Gateway

Choose Two System IDs for Each Microsoft SQL Server Database

A separate instance of the gateway accesses the different Microsoft SQL Server databases. Each instance needs its own gateway System ID (SID). For this example, the gateway SIDs are chosen for the instances that access the Microsoft SQL Server databases:

• tg4msql2 for the gateway accessing database db2

• tg4msql3 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\tg4msql\admin\inittg4msql.ora, twice, naming one with the gateway SID for db2 and the other with the gateway SID for db3:

> cd ORACLE_HOME\tg4msql\admin
> copy inittg4msql.ora inittg4msql2.ora
> copy inittg4msql.ora inittg4msql3.ora

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

For inittg4msql2.ora, enter the following:

HS_FDS_CONNECT_INFO=msql_nt2.db2

For inittg4msql3.ora, enter the following:

HS_FDS_CONNECT_INFO=msql_nt3.db3

2.6.2 Multiple Databases Example: Configuring Oracle Net Services Listener

Add Entries to listener.ora

Add two new entries to the TNS 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=tg4msql)
      (ORACLE_HOME=oracle_home_directory)
      (PROGRAM=tg4msql)
   )
   (SID_DESC=
      (SID_NAME=tg4msql2)
      (ORACLE_HOME=oracle_home_directory)
      (PROGRAM=tg4msql)
   )
   (SID_DESC=
      (SID_NAME=tg4msql3)
      (ORACLE_HOME=oracle_home_directory)
      (PROGRAM=tg4msql)
   )
)

2.6.3 Multiple Databases Example: Stopping and Starting the TNS Listener

1. Select Services from the Windows Control Panel. (For example, for Windows 2000, from the Windows Start menu select Settings,Control Panel, Administrative Tools, and then select Services.)

2. Select the TNSListener service for the gateway.

3. Click Stop.

4. Click Start.

2.6.4 Multiple Databases Example: Configuring the Oracle Database Server for Gateway Access

old_db_using=(DESCRIPTION=
              (ADDRESS=
                (PROTOCOL=TCP)
                (PORT=1541)
                (HOST=gtwhost))
                (CONNECT_DATA=
                    (SID=tg4msql))
               (HS=OK))
new_db2_using=(DESCRIPTION=
              (ADDRESS=
                (PROTOCOL=TCP)
                (PORT=1541)
                (HOST=gtwhost))
                (CONNECT_DATA=
                    (SID=tg4msql2))
                (HS=OK))
new_db3_using=(DESCRIPTION=
              (ADDRESS=
                (PROTOCOL=TCP)
                (PORT=1541)
                (HOST=gtwhost))
                (CONNECT_DATA=
                    (SID=tg4msql3))
                (HS=OK))

2.6.5 Multiple Databases Example: Accessing Microsoft SQL Server Data

Enter the following to create a database link for the tg4msql2 gateway:

SQL> CREATE PUBLIC DATABASE LINK MSQL2 CONNECT TO
  2  user2 IDENTIFIED BY password2 USING 'new_db2_using';

Enter the following to create a database link for the tg4msql3 gateway:

SQL> CREATE PUBLIC DATABASE LINK MSQL3 CONNECT TO
  2  user3 IDENTIFIED BY password3 USING 'new_db3_using';

After the database links are established you can query the new Microsoft SQL Server databases, as in the following:

SQL> SELECT * FROM ALL_USERS@MSQL2;

or

SQL> SELECT * FROM ALL_USERS@MSQL3;

2.7.1 Configuring for Two-Phase Commit

The gateway supports the following transaction capabilities:

• COMMIT_CONFIRM

• READ_ONLY

• SINGLE_SITE

• TWO_PHASE_COMMIT

By default, the gateway runs in COMMIT_CONFIRM transaction mode. When the Microsoft SQL Server database is updated by a transaction, the gateway becomes the commit point site. The Oracle database server commits the unit of work in the Microsoft SQL Server database after verifying that all Oracle databases in the transaction have successfully prepared the transaction. Only one gateway can participate in an Oracle two-phase commit transaction as the commit point site.

To enable the COMMIT_CONFIRM transaction mode, create a recovery account and password and create a log table. The log table, called by default HS_TRANSACTION_LOG, is where two-phase commit transactions are recorded.

> isql -Urecovery_account -Precovery_account_password [-Sserver] -itg4msql_tx.sql

2.7.2 Specifying an Owner

Instead of using the default owner name for the Microsoft SQL Server tables as defined in Microsoft SQL Server, or explicitly specifying a different owner in the SQL statements, you can specify a default owner that is used whenever a name is not explicitly specified in the SQL statements.

To specify the owner, set the gateway initialization parameter HS_FDS_DEFAULT_OWNER in the initialization parameter file.