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Oracle Net

Oracle Net is a component of the Oracle server providing distributed database and processing capabilities. Oracle Net for OS/390 supports network communications between Oracle applications and Oracle9i database server systems across different OS/390 systems or foreign operating systems.

This chapter discusses usage considerations for Oracle Net on OS/390 and covers OS/390 clients (including servers that initiate database links) accessing remote Oracle servers as well as remote clients accessing a Oracle server on OS/390. It contains the following sections:

• Oracle Net Overview

• Remote Access to OS/390 Server Using Oracle Net

• Oracle Net and OS/390 Clients

For product-specific information, refer to the Oracle9i Net Services Administrator's Guide.

See Chapter 2, "Using the OS/390 Database Instance", for information about accessing an Oracle instance from a local client. For information about accessing a remote Oracle instance from USS, see Chapter 4, "Accessing Oracle9i Under USS".

Oracle Net Overview

The Oracle Net Network Service acts as the bridge between Oracle clients and servers and the communication facilities of the OS/390 operating system, thus supporting network communications between Oracle applications and Oracle9i database server systems or gateways across different images or operating systems. One protocol is available: TCP/IP. The Oracle Net Network Service is controlled via the parameters in its service definition.

Distributed Processing

Dividing processing between a front-end computer running an application and a back-end computer used by the application is known as distributed processing. Oracle Net enables an Oracle tool or application to connect to a remote computer supporting an Oracle9i database server or gateway.

Distributed Database

Several databases linked through a network, appearing to a user as a single logical database, are known as a distributed database. Oracle tools running on a client computer can share and obtain information retrieved from other remote Oracle9i database servers or gateway systems. Regardless of the number of database information sources, the user may only be aware of one logical database.

Oracle Net Terminology

The following terms are used to explain the architecture of Oracle Net for OS/390:

Host	is the computer on which the database resides. It runs the Oracle9i database server or an Oracle gateway.
Server	is the Oracle9i database service.
Client	is the application using Oracle Net to communicate with a server. A server is also considered a client if it initiates a connection with another server.
Protocol	is a set of standards governing the operation of a communication link.
Network	is a configuration of devices and software connected for information interchange.

Remote Access to OS/390 Server Using Oracle Net

Remote (inbound) clients access Oracle9i for OS/390 database instances through Oracle Net using Oracle Net address strings as follows:

1. Oracle Net listens on a single endpoint (network address) for each protocol. All remote clients that go through a particular network service with a particular protocol use the same network address regardless of which database instance they want to access. All TCP/IP clients specify the same hostname (or IP) and port number.

2. Clients indicate the target database instance that they want with the '(CONNECT_DATA=(SID=sid))' clause in the Oracle Net address string. This is required with Oracle Net for OS/390.

Oracle Net and OS/390 Clients

Outbound OS/390 clients (including servers that initiate database links) that are connecting to remote Oracle database instances via Oracle Net for OS/390 must specify the SSN= parameter in the Oracle Net address string or a TNS@ssss DD allocation in the address space to specify a SID that is associated with an OSDI network service. Note that the network service SID is 4 characters or less.

Oracle clients on OS/390 must also allocate appropriate Oracle Net files to specify TNSNAMES connect descriptors as well as Oracle Net parameters.

Oracle Net for OS/390 Filenames

Oracle Net for OS/390 supports a number of Oracle Net files that are used to specify TNSNAMES connect descriptors as well as Oracle Net parameters. The Oracle Net parameters are used to configure Oracle Net processing options for Oracle Net facilities such as Name Server, LDAP as well as Oracle Net logging.

The base Oracle Net documentation, Oracle9i Net Services Administrator's Guide, refers to files in the following form:

basename.extension

where basename is the product name and extension is the extension.

An example of this form is SQLNET.ORA.

These files are mapped to DDnames on OS/390. The following DDnames are implemented under OS/390:

SQLNET	defines a data set containing any SQLNET.ORA diagnostic, ASO, or Oracle Names parameters. It is not necessary to allocate this DD unless these features are desired. Refer to Oracle9i Net Services Administrator's Guide or the Oracle Advanced Security Administrator's Guide for more information.
SQLNETLG	defines a data set into which any logging output is written. Oracle Corporation recommends that this be defined as a SYSOUT data set in a held output class.
SQLNETTC	defines a data set into which any logging output is written. Oracle Corporation recommends that this be defined as a SYSOUT data set in a held output class.
TNSNAMES	defines a data set containing all the TNS connect descriptors and aliases for your installation. For further information on TNS connect descriptors, refer to the Oracle9i Net Services Administrator's Guide. This DDname is not necessary on server JCL unless DBLINKS originate from the server.
LDAP	defines the location of the LDAP server.
TNSNAV	TNS client navigation. (Generally not used on OS/390.)
INTCHG	Interchange. (Generally not used on OS/390.)

Locating the Oracle Net Service

Clients (including servers that initiate database links) that use Oracle Net for OS/390 to access servers across a TCP/IP network must specify the Oracle Net service to be used for the connection. This can only be done in one of two ways:

1. Specify the (SSN=ssss) parameter in the connect string. An example of this is shown in the next section.

2. Specify a 'TNS@ssss DD DUMMY" card on the JCL of the batch client (or database link server), or dynamically allocate such a DD for a TSO session.

   In both of these examples, ssss represents the service identifier of the desired Oracle Net service. There is no 'default' Oracle Net service identifier, thus a connect that does not specify the Oracle Net service using one of these two methods will fail.

Oracle Net Connect Descriptors for OS/390

The Oracle Net connect descriptors for OS/390 adopts the same syntax as the base Oracle Net connect descriptors with one exception; the SSN= parameter described. Note that the SSN= parameter is optional and is only required if a TNS@ssss DDname is not specified.

TCP/IP Addresses

The syntax for the TCP/IP address portion of a connect descriptor on OS/390 is described as follows:

aliasname=
          (DESCRIPTION=
           (ADDRESS=
            (PROTOCOL = TCP) 
            (HOST = hostname) 
            (PORT = port_num) 
            (SSN=ssss))
            (CONNECT_DATA=(SID=sid)))

where:

aliasname	is the name used to reference this connection description.
hostname	is the host nickname as defined to TCP/IP or the host internet address as a decimal value.
port_num	is the TCP/IP port number on which the target database is listening.
ssss	is the SID from the service definition for the Oracle Net service through which the connection can be made. This parameter is valid only on OS/390.
sid	is the SID of the target Oracle server.

Examples

Connecting to a Remote Server Using Oracle Net

To use Oracle Net for OS/390 in client mode, the connect string must include an alias defined in the TNSNAMES file or a valid TNS connect descriptor.

• To use the descriptors defined in the TNSNAMES file in a TSO session, allocate:

  ALLOC F(TNSNAMES) DA('ORA.SQLNET.CNTL(tnsname)') SHR REUSE
  

• To connect to a remote database with an alias of ORAUNIX using SQL*Plus, the following connect string can be used:

  SQLPLUS SCOTT/TIGER@ORAUNIX 
  

  The definition for alias ORAUNIX is defined in the data set allocated to DDname TNSNAMES with:

  ORAUNIX=
          (DESCRIPTION=
          (ADDRESS=
          (PROTOCOL=TCP)
          (HOST=HQUNIX)
          (PORT=1533)
          (SSN=TNS))
          (CONNECT_DATA=
          (SID=UNIX)))
  

  Note: A DD definition of TNS@TNS can be used instead of the SSN= parameter shown above. Both of these assumes that the Oracle Net service name is TNS, or a SID of TNS was included in the service definition for Oracle Net. Oracle Corporation recommends you define all your databases in a public data set accessible by all users so they can connect to databases using aliases instead of TNS connect descriptors.

Oracle Names and LDAP

Oracle clients on OS/390 can use an Oracle Names or LDAP server running on another platform to resolve connection requests. The following samples of the Oracle Net configuration file is required to make use of these services. Please note that a TNS@ssn DD card is necessary.

Name Server

SQLNET DD or SQLNET.ORA Definitions:
###############
# Names .........: (CONNECT_TIMEOUT = 0) -MUST- be specified
###############
NAMES.DEFAULT_DOMAIN = world
NAMES.DEFAULT_ZONE = my.domain.com
NAMES.DIRECTORY_PATH = (TNSNAMES,ONAMES, LDAP)
NAMES.PREFERRED_SERVERS =
(ADDRESS_LIST =
(DESCRIPTION =
(ADDRESS =
(PROTOCOL = TCP)
(HOST = names_host)
(Port = 1575)
)
(CONNECT_TIMEOUT = 0)
)
)

LDAP Server

LDAP DD or LDAP.ORA Definitions:
A sample LDAP.ORA file:
DEFAULT_ADMIN_CONTEXT = "c=us"
DIRECTORY_SERVERS = (hostname:389:636)
DIRECTORY_SERVER_TYPE = OID, LDAP after ONAMES

LDAP.ORA can be generated using the NETCA utility.