Ingres® 2006 for OpenVMS - RMS Gateway User Guide

Peter Kitson

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Sample Chapter From Ingres® 2006 for OpenVMS - RMS Gateway User Guide
     Copyright © Ingres Corporation



Chapter 1: Introducing the RMS Gateway

The RMS gateway allows Ingres® users transparent access from various client applications to data stored in OpenVMS RMS files.

Ingres users on a client can develop database applications on an OpenVMS platform, which can be executed against RMS data without requiring additional programming.

RMS Gateway

The RMS gateway lets you use the Ingres tools to query, update, and create data stored in RMS files. The gateway provides full read and write capabilities. The RMS gateway is part of an RMS gateway data manager—similar to the standard Ingres data manager—that lets Ingres manipulate data in RMS files as relational data in Ingres tables. The RMS gateway performs all supported Ingres data manipulation functions, such as retrieving, updating or inserting data.

To use the RMS gateway, you must install an RMS gateway data manager, even if your site already has a standard Ingres data manager (that is, a data manager that lets you access data stored in Ingres databases).

How the RMS Gateway Works

The RMS gateway lets you represent data records in RMS files as rows in Ingres tables, using the full relational capabilities of Ingres. The RMS gateway resides in the RMS gateway data manager process as part of the GenericGateway Facility (GWF). The GWF, which is an extension of the Data Manipulation Facility (DMF) component of the data manager, allows physical access to non-Ingres data files.

To access RMS data through the gateway, you must define the data to Ingres by creating an RMS gateway database in which you register your RMS data as Ingres tables and indexes. This database has the extension /rms so that the data manager knows that it is an RMS gateway database.

An RMS gateway database does not contain any RMS data. It holds only the catalog entries for the underlying RMS data—that is, the RMS data files and indexes that you have registered in the database. These catalog entries tell the gateway:

  •   Where the underlying data is located
  •   What the data looks like
  •   How data is mapped to Ingres databases and tables

This guide describes how to register RMS data and access the data through the RMS gateway.

Gateway Query Processing

When you submit a query to the RMS gateway server process, most components of the data manager treat the query as though it were accessing Ingres data. However, the data manager knows that you are connected to a gateway database because of the /rms extension.

In this way, the data manager’s Data Manipulation Facility (DMF) can make the proper calls to the gateway facility. For example, when a table in a gateway database is opened, the DMF open routine calls the gateway routine that uses the RMS function to open the file. Similarly, when data is requested, the DMF read routine calls the gateway routine to obtain the data from the RMS file.

After the gateway exit routine is completed successfully, the data is converted to Ingres data types and looks as though it comes from an Ingres table.