5 Oracle Net

Distributed Processing

Dividing processing between a front-end computer that is running an application and a back-end computer that is used by the application is known as distributed processing. Oracle Net enables an Oracle tool or application to connect to a remote computer containing an Oracle server or Oracle gateway.

Distributed Database

Several databases that are linked through a network and that appear as a single logical database are known as a distributed database. An Oracle tool running on a client computer or on an Oracle server running on a host computer can share and obtain information that is retrieved from other remote Oracle servers or Oracle gateways. Regardless of the number of database information sources, you might be aware of only one logical database.

Terminology for Oracle Net

The following terms are used to explain the architecture of Oracle Net for AS/400:

host: is the computer on which the database resides and the computer that runs the Oracle gateway. On AS/400, only a gateway can be running. The Oracle Database does not run on the AS/400.

client (task): is the application using an Oracle Net driver to communicate with the Oracle Database server or gateway. A server is also considered to be a client if it initiates a connection with another Oracle Database server, or with an Oracle gateway.

protocol: is a set of standards or rules governing the operation of a communication link.

driver: is the part of Oracle Net that supports a given network protocol or communication method.

network: is a configuration of devices and software that are connected in order to interchange information.

Oracle Net for AS/400 Architecture

Oracle Net connections are established on the AS/400 through a listener. A listener receives incoming connections from Oracle Net clients and starts or transfers to a job on the AS/400 system.

On the AS/400, the Oracle Net TNS listener is used for TCP/IP.

Figure 5-1 shows communication between a client and the AS/400. Oracle Net on the AS/400 can accept TCP/IP connections.

Figure 5-1 Oracle Net Communication to the OS/400

After the listener accepts the client connection, a batch job is started on the AS/400, or (more usually) a prestarted AS/400 batch job receives control. The batch job executes the gateway and sends a response back to the client. The response is data or a message. Each batch job is responsible for a client connection. Only one batch job is executed for a single connection, and a single connection is associated with only one batch job.

To reduce the waiting time for connecting to gateway jobs, a set of prestarted gateway batch jobs are associated with a TNS listener. The number of prestarted jobs and the point at which additional jobs are started can be modified by the system administrator.

File Name Structure

Oracle Net refers to files in the following format:

basename.extension

where basename is the base portion of the name, and extension is the second part of the name.

An example of this form is SQLNET.ORA.

On the AS/400, the Oracle Net parameter files are installed in the gateway instance library using the following file name mapping:

• The base portion of the file name is mapped to a member name in an AS/400 file.

• The extension portion of the file name is mapped to an AS/400 file name.

For example, the SQLNET.ORA parameter file is mapped to member SQLNET in the ORA file that is located in the gateway instance library. Member names are referred to as:

file(member_name)

Some of the parameter values in ORA(SQLNET) can be changed with the CHGORANET command. For more information, refer to "CHGORANET, Change Network Parameters".

For a list of the network files and members that are provided with the gateway, refer to Appendix A, "Oracle Net Files and Members".

Step 1: Add a TCP/IP Connect Descriptor to tnsnames.ora

Use the TCP/IP connect descriptor in the tnsnames.ora file on the Oracle Database 10g server:

connect_name = (DESCRIPTION=
                (ADDRESS=(PROTOCOL=TCP)
                  (PORT=1521)
                  (HOST=host_name)
                )
                (CONNECT_DATA=(SID=csi_name))
              (HS=)
              )

where:

connect_name is the name of the connection. This name must be unique within the tnsnames.ora file. The connect_name corresponds to the value that is found with the USING keyword on a CREATE DATABASE LINK command.

TCP is the TCP protocol that is used for TCP/IP connections.

1521 is the default port number that is used by the Oracle Net listener on the AS/400. Change this value if you have changed the listener port number.

host_name is the TCP/IP host name of your AS/400 computer. It may be a DNS name, such as myas400.us.mycompany.com or an IP dotted value such as 10.2.3.7.

csi_name is the name of the communication side information (*CSI) file that is used by the listener to start the server. Usually, the csi_name is ORAGATE. Refer to "Step 2: Specify SID Names" for more SID names.

HS= This keyword is mandatory. The right-hand side of the HS keyword is not needed.

Step 2: Specify SID Names

Oracle servers that are using TCP/IP to connect to a gateway must specify a system identifier (SID) name in the TNSNAMES.ORA file that is used to connect to the AS/400. The SID name is used on the AS/400 to start the server. The listener uses the SID name to reference a *CSI file. The *CSI file uses a TP_NAME to start the required CL program in the gateway server. Several SID names are configured in the shipped system and are listed in the following table.

Set the SID to ORAGATE in order to use a prestarted job. ORAGATE would give the best response time. Setting the SID to other values should be done in special situations as directed by Oracle support personnel.

The following table provides the name and usage of each SID:

Refer to "Viewing Jobs" for instructions on viewing jobs and a description of the jobs that typically exist.

Checklist for Configuring Oracle Net for TCP/IP

• Step 1: Configure the Port Number

• Step 2: Define the Host Name

• Step 3: Verify the Host Name

• Step 4: Verify that the Listener is Started

Connecting Through TCP/IP (on the Oracle Server) Checklist

• Step 1: Add a TCP/IP Connect Descriptor to tnsnames.ora

• Step 2: Specify SID Names

Preliminary Step: Define a Physical Line

This step is required only if no physical connection currently exists between the Oracle Database 10g server and the AS/400.

To define the physical connection, use the CRTLINETH command to create an ethernet connection.

When you use the CRTLINETH command, you can set the AUTOCREATE CONTROLLER parameter to *YES (the AS/400 system default is *NO). This enables the AS/400 auto configuration feature.

If a line is already defined, then you can use the DSPLIND line_name command to display the line description parameters.

These line description parameters are used to configure the network on the computer where the gateway resides.

Configuring for TCP/IP

Perform the following steps to configure your TCP/IP connection between the Oracle Database 10g server and the AS/400:

Step 1: Configure the Port Number

Step 2: Define the Host Name

Step 3: Verify the Host Name

Step 4: Verify that the Listener is Started

Step 1: Configure the Port Number

If the gateway is already assigned to port 1521 or to another available port number, then go to "Step 2: Define the Host Name".

The gateway listener must be assigned a dedicated port number on which to listen for incoming connection requests. The default port number is 1521. This number can be changed during installation if you know that port 1521 is already used or if you prefer to use a different port number for any other reason. The port number may also be changed after installation by using the CHGORANET command.

You can find the values of port numbers that are currently active by using the AS/400 command NETSTAT *CNN. Each running instance requires a unique listener port number. Two gateway instances that are active at the same time cannot use the same listener port number. For more information, refer to "CHGORANET, Change Network Parameters".

Step 2: Define the Host Name

To define the host name, perform the following steps:

1. Run the AS/400 CFGTCP command.

2. Select option 12, Change TCP/IP domain information. The panel in Example 5-1, "Change TCP/IP Domain (CHGTCPDMN)" is displayed:

___________________________________________________________________________________________________
                           Change TCP/IP Domain (CHGTCPDMN)

         Type Choices, press Enter.

         Host name...                       'AS400A'
         Domain name...                     'US.ORACLE.COM'
         Domain search list...              *DFT
         Host name search priority...       *REMOTE   *REMOTE,  *LOCAL,  *SAME
         Domain name server
           Internet address...              '140.24.88.144'
                                            '140.24.244.29'


                                                                         Bottom

         F3=Exit  F4=Prompt  F5=Refresh  F10=Additional parameters  F12=Cancel
         F11=How to use this dispay  F24=More Keys

___________________________________________________________________________________________________

1. Enter your domain name if the Domain name field is empty. Enter your host name if the Host name field is empty.

   Press Enter to save your changes and return to the option list panel. (The changes take effect after you restart the gateway.)

   The host name and the domain name combine to form the qualified host name. For example, AS400A combines with US.ORACLE.COM to form AS400A.US.ORACLE.COM as the qualified host name.

Step 3: Verify the Host Name

Verify that your host name is in your host name table by using the following AS/400 command:

PING host_name.domain_name

You can also use a PING command on the client-side Oracle Database server to verify that it can communicate with the OS/400.

Step 4: Verify that the Listener is Started

Use the Oracle Gateway Monitor to verify that the listener is started. If it is necessary to start the listener, then use the Oracle Gateway Monitor to do so, or start the listener manually with the following command:

STRORALSN

You can use the NETSTAT *CNN command to verify that the port that is assigned to the LISTENER is, in fact, being used by the LISTENER job in a given gateway instance. For more information about using the Oracle Gateway Monitor, refer to Chapter 8, "Administering the Gateway".

AS/400 Connection Problems

The following suggestions may resolve your connection problems:

ORA-28509

The following are some causes of the error.

ORA-28511

The following are some causes of the error.

ORA-28500

Check any accompanying message from the AS/400 to determine what the problem might be, or check the AS/400 job log (RUNORAGTTP job log). For example, message SQL-7008 indicates that the file is not journaled.

ORA-12154

This error indicates that a missing or incorrect tnsnames file has been specified, or that an incorrect spelling or service name has been specified in the tnsnames file. This is generally an Oracle Net issue, not a gateway issue.

Option 10 of CFGTCP: Work with TCP/IP Host Table Entries

Enter Internet addresses and host names. Host names in the "Work with TCP/IP Host Table Entries" panel must include both the unqualified and the qualified names (the one that includes the domain name).

Option 10 depends upon Option 12. Option 12 defines your host name as well as your domain name. Under Option 10, you must enter your host name and your hostname.domain_name. This may seem redundant, but if the gateway is not configured correctly for TCP/IP, then the gateway will not make a connection, regardless of the output from the PING command. Any changes to CFGTCP will require you to restart the gateway.

TCP configuration is documented in "Configuring Oracle Net for TCP/IP AS/400" in this chapter.

Option 12 of CFGTCP: Change TCP/IP Domain (CHGTCPDMN)

The host name and the domain name combine to form the qualified host name. For example, AS400A (as illustrated in Option 12) combines with "US.ORACLE.COM" to form the qualified host name AS400A.US.ORACLE.COM.