The Oracle Database Gateway for APPC extends the Remote Procedural Call (RPC) facilities available with the Oracle database . The gateway enables any client application to use PL/SQL to request execution of a remote transaction program (RTP) residing on a host. The gateway provides RPC processing to systems using the SNA APPC (Advanced Program-to-Program Communication) protocol and to systems using TCP/IP for IMS Connect protocol. This architecture allows efficient access to data and transactions available on the IBM mainframe and IMS, respectively.

The gateway requires no Oracle software on the remote host system. Thus, the gateway uses existing transactions with little or no programming effort on the remote host.

The Oracle Database Gateway for APPC provides the following benefits:

• TCP/IP support for IMS Connect

  This release of the gateway includes TCP/IP support for IMS Connect, giving users a choice of whether to use the SNA or TCP/IP communication protocol. IMS Connect is an IBM product which allows TCP/IP clients to trigger execution of IMS transactions. The gateway can use a TCP/IP communication protocol to access IMS Connect, which triggers execution of IMS transactions. If you choose to use TCP/IP, then there is no SNA involvement with this configuration. Related to this new feature of the gateway is:

  • The pg4tcpmap tool. This release of the gateway includes a new tool whose purpose is to map the information from your side profile name to TCP/IP and IMS Connect. For more information about the gateway mapping tool, refer to Chapter 6, of the Oracle Database Gateway for APPC User's Guide, and to Gateway Configuration Using TCP/IP Communication Protocol in this guide.

• Fast interface

  The gateway is optimized so that remote execution of a program is achieved with minimum network traffic. The interface to the gateway is an optimized PL/SQL stored procedure specification (called the TIP or transaction interface package) precompiled in the Oracle database . Because there are no additional software layers on the remote host system, overhead occurs only when the program processes.

• Location transparency

  Client applications need not be operating system-specific. For example, your application can call a program on a CICS Transaction Server for z/OS. If you move the program to a CICS region on pSeries, then you need not change the application.

• Application transparency

  Users calling applications that execute a remote transaction program are unaware that a request is sent to a host.

• Flexible interface

  You can use the gateway to interface with existing procedural logic or to integrate new procedural logic into an Oracle database environment.

• Oracle database integration

  The integration of the Oracle database with the gateway enables the gateway to benefit from existing and future Oracle features. For example, the gateway can be called from an Oracle stored procedure or database trigger.

• Transactional support

  The gateway and the Oracle database allow remote transfer updates and Oracle database updates to be performed in a coordinated fashion.

• Wide selection of tools

  The gateway supports any tool or application that supports PL/SQL.

• PL/SQL code generator

  The Oracle Database Gateway for APPC provides a powerful development environment, including:

  • a data dictionary to store information relevant to the remote transaction

  • a tool to generate the PL/SQL Transaction Interface Package, or TIP

  • a report utility to view the information stored in the gateway dictionary

  • a complete set of tracing and debugging facilities

  • a wide set of samples to demonstrate the use of the product against datastores such as DB2, IMS, and CICS.

• Site autonomy and security

  The gateway provides site autonomy, allowing you to do such things as authenticate users. It also provides role-based security compatible with any security package running on the mainframe computer.

• Automatic conversion

  Through the TIP, the following conversions are performed:

  • ASCII to and from EBCDIC

  • remote transaction program datatypes to and from PL/SQL datatypes

  • national language support for many languages

The following terms and definitions are used throughout this guide. Refer to Gateway Terminology for a more elaborate list of terms and definitions pertaining to the gateway, its components and functions.

The architecture of Oracle Database Gateway for APPC consists of several components:

• Oracle database

• The gateway

  Oracle Database Gateway for APPC must be installed on a server that can run the required version of the operating system.

• An OLTP

  The OLTP must be accessible from the gateway using the SNA or TCP/IP communication protocol. Multiple Oracle database s can access the same gateway. A single system gateway installation can be configured to access more than one OLTP.

• For a gateway using TCP/IP support for IMS Connect: The only OLTP that is supported through TCP/IP is IMS through IMS Connect.

  The OLTP must be accessible to the system using the TCP/IP protocol. Multiple Oracle database s can access the same gateway. A single-system gateway installation can be configured to access more than one OLTP. Multiple IMS can be accessed from an IMS Connect. If you have a number of IMS Connect systems available, then any of these may be connected to one or more IMS systems.

Figure 1-2 illustrates the architecture of Oracle Database Gateway for APPC using either SNA or TCP/IP, as described in the preceding section.

The basic structure of the gateway is the same whether your communications protocol is SNA or TCP/IP support for IMS Connect. The gateway has some of the same components as an Oracle database instance on Microsoft Windows. It has the following components:

• a home directory, similar to the one associated with an Oracle instance's ORACLE_HOME environment variable;

• a system identifier, identified as sid or ORACLE_SID;

• an initialization parameter file, similar to the Oracle database 's initsid.ora file.

The gateway does not have:

• control, redo log, or database files;

• the full set of subdirectories and ancillary files associated with an installed Oracle database .

Because the gateway has no background processes and does not need a management utility such as Oracle Enterprise Manager, you do not need to start the gateway product. Each Oracle database user session that accesses a particular gateway creates an independent process on Windows, which, in turn, runs the gateway server and executes either the SNA or TCP/IP functions to communicate with an OLTP.

All of the communication between the user or client program and the gateway is handled through a TIP which executes on an Oracle database . The TIP is a standard PL/SQL package that provides the following functions:

• declares the PL/SQL variables that can be exchanged with a RTP;

• calls the gateway packages that handle the communications for starting the conversation, exchanging data, and terminating the conversation;

• handles all datatype conversions between PL/SQL datatypes and the target program datatypes.

The PGAU, provided with the gateway, automatically generates the TIP specification.

The gateway is identified to the Oracle database using a database link. The database link is the same construct used to identify other Oracle databases. The functions in the gateway are referenced in PL/SQL as:

function_name@dblink_name 

The Oracle Database Gateway for APPC provides a set of functions that are invoked by the client through remote procedural call (RPC). These functions direct the gateway to initiate, transfer data with, and terminate RTPs running under an OLTP on another system.

Table 1-1 lists the RPC functions and the correlating commands that are invoked in the gateway and remote host.

The Oracle Database Gateway for APPC supports three types of transactions that read data from and write data to remote host systems:

• one-shot

  In a one-shot transaction, the application initializes the connection, exchanges data, and terminates the connection, all in a single call.

• persistent

  In a persistent transaction, multiple calls to exchange data with the remote transaction can be executed before terminating the conversation.

• multiconversational

  In a multiconversation transaction, the database gateway server can be used to exchange multiple records in one call to the RTP.

Refer to "Remote Host Transaction Types" in Chapter 4, "Client Application Development" of the Oracle Database Gateway for APPC User's Guide for more information about transaction types.

The following list demonstrates the power of the Oracle Database Gateway for APPC:

• You can initiate a CICS transaction on the mainframe to retrieve data from a VSAM file for a PC application.

• You can modify and monitor the operation of a remote process control computer.

• You can initiate an IMS/TM transaction that executes static SQL in DB2.

• You can initiate a CICS transaction that returns a large number of records in a single call.

The Oracle Database Gateway for APPC using TCP/IP for IMS Connect supports three types of transaction socket connections:

• transaction socket

  The socket connection lasts across a single transaction.

• persistent socket

  The socket connection lasts across multiple transactions.

• nonpersistent socket

  The socket connection lasts across a single exchange consisting of one input and one output.

  Note:

  Do not use the nonpersistent socket type if you plan on implementing conversational transactions because multiple connects and disconnects will occur.

  Refer to the section about pg4tcpmap commands in Chapter 6 of the Oracle Database Gateway for APPC User's Guide and to Gateway Configuration Using TCP/IP Communication Protocol in this guide for more information about how to enter these parameters.

  You can initiate an IMS/TM transaction that executes static SQL in DB2, this illustrates the power of the Oracle Database Gateway for APPC feature supporting TCP/IP for IMS Connect.