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Oracle® Transparent Gateway for Microsoft SQL Server Administrator's Guide
10g Release 1 (10.1) for Microsoft Windows

Part Number B10544-01
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2
Configuring the Gateway

After installing the gateway, perform the following tasks to configure the gateway for Microsoft SQL Server:

Configuring the Gateway

Perform the following tasks to configure the Oracle Transparent Gateway for Microsoft SQL Server.

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.

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 Windows NT 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.

See Also:

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

Configuring Oracle Net Services Listener for the Gateway

The gateway requires Oracle Net Services to provide transparent data access. After configuring the gateway, configure Oracle Net Services to work with the gateway.

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.


Note:

If Oracle Net Services is reinstalled, the original listener.ora file is renamed and a new listener.ora file is put into the ORACLE_HOME\network\admin directory.


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

Example of Address to Listen On in listener.ora File

The Oracle database server accesses the gateway using Oracle Net Services and the TCP/IP protocol adapter. The following is the syntax of the connect descriptor entry in the listener.ora file:

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

where:

Parameter Description

host_name

is the name of the machine on which the gateway is installed.

port_number

specifies the port number used by the TNS listener. If you have other listeners running on host_name, the value of port_number must be different from the other listeners' port numbers.

Example of Gateway to Start in listener.ora File

To direct the TNS listener to start the gateway in response to incoming connection requests, add an entry to the listener.ora file with the following syntax:

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

where:

Parameter 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.

tg4msql

specifies the Oracle Transparent Gateway for Microsoft SQL Server.

If you are already running a TNS listener that listens on multiple database SIDs, add only the following syntax to SID_LIST in the existing listener.ora file:

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

See Also:

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

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 > 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.

Configuring the Oracle Database Server for Gateway Access

Before you use the gateway to access Microsoft SQL Server data you must configure the Oracle database server to enable communication with the gateway over Oracle Net Services.

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.

See Also:

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

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.

Configuring tnsnames.ora

Edit the tnsnames.ora file to add a connect descriptor for the gateway. The following is an example of the Oracle Net Services entries using TCP/IP protocol needed for the Oracle database server to access the gateway:

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

where:

Parameter Description

connect_descriptor

is the description of the object to connect to as specified when creating the database link, such as tg4msql.

Check the sqlnet.ora file in the Oracle database server's ORACLE_HOME for the following lines:

  • names.directory_path = (TNSNAMES, HOSTNAME)

  • names.default_domain = world

  • name.default_zone = world

Note: If the Oracle database server is on Microsoft Windows NT, the file is ORACLE_HOME\network\admin\sqlnet.ora.

If the sqlnet.ora file has these lines, connect_descriptor must end with the extension .world.

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 Services TNS listener that is listening for the gateway. The TNS listener's port number can be found in the listener.ora file used by the TNS listener. See "Example of Address to Listen On in listener.ora File".

gateway_sid

specifies the SID of the gateway and matches the SID specified in the listener.ora file of the TNS listener that is listening for the gateway. See "Task 1: Configure Oracle Net Services TNS Listener for the Gateway" for more information.

(HS=OK)

specifies that this connect descriptor uses the Oracle Heterogeneous Services option.

Creating Database Links

Any Oracle client connected to the Oracle database server can access Microsoft SQL Server data through the gateway. The Oracle client and the Oracle database server can reside on different machines. The gateway accepts connections only from the Oracle database server.

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 server 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 Microsoft SQL Server 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. The database and application administrators of a distributed database system are responsible for managing the necessary database links that define paths to the Microsoft SQL Server database.

See Also:

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

Configuring the Gateway for Multiple Microsoft SQL Server Databases

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

Configuring the gateway for additional Microsoft SQL Server databases is similar to configuring it for one database, and involves the following:

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:

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


Note:

If you have multiple gateway SIDs for the same Microsoft SQL Server 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.


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)
   )
)

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 > Services.)

  2. Select the TNSListener service for the gateway.

  3. Click Stop.

  4. Click Start.

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

Configuring Oracle Net Services on the Oracle Database Server 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 Microsoft SQL Server 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=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))

The value for PORT is the TCP/IP port number of the TNS listener that is listening for the gateway. The number can be found in the listener.ora file used by the TNS 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 TNS listener.

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;

Performing Configuration Tasks

You can perform the following configuration tasks:

Configuring for Two-Phase Commit

The gateway supports the following transaction capabilities:

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.

See Also:

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

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.

Task 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 Microsoft SQL Server 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 use the default value RECOVER for the user name and password.


  1. Set up a user account in the Microsoft SQL Server database. Both the user name and password must be a valid Microsoft SQL Server user name and password.

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

Task 2: Create the Transaction Log Table

When configuring the gateway for two-phase commit, a table must be created in the Microsoft SQL Server database for logging transactions. The gateway uses the transaction log table to check the status of failed transactions that were started at the Microsoft SQL Server 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 D, "Heterogeneous Services Initialization Parameters" for information about the HS_FDS_TRANSACTION_LOG initialization parameter.

Create the transaction log table in the user account you created in "Task 1: 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 Microsoft SQL Server 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 tg4msql_tx.sql script, located in the directory ORACLE_HOME\tg4msql\admin where ORACLE_HOME is the directory under which the gateway is installed. Use isql to execute the script at the MS-DOS prompt, as follows:

> isql -Urecovery_account -Precovery_account_password [-Sserver] -itg4msql_
tx.sql

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.

See Also:

Appendix D, "Heterogeneous Services Initialization Parameters" for information about the HS_FDS_DEFAULT_OWNER initialization parameter.


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