Oracle Database Gateway for Informix 11g Release 2用户指南

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Oracle Database Gateway for Informix是一款专为Informix数据库提供与Oracle数据库集成的中间件解决方案。此用户指南适用于Oracle数据库11g Release 2 (11.2)版本，文档编号为E12066-02，发布日期为2012年1月。该文档由Maitreyee Chaliha为主要作者，其他贡献者包括Vira Goorah、Juan Pablo Ahues-Vasquez、Peter Castro、Charles Benet、Peter Wong和Govind Lakkoju等。 Oracle Database Gateway for Informix的主要功能是允许在Oracle数据库和Informix数据库之间无缝的数据交换和操作。它通过建立一个桥接，使得两个不同类型的数据库系统能够相互访问数据，实现了异构数据库环境下的数据共享。这个工具支持多种数据库操作，如查询、更新、插入和删除，使得开发人员无需深入理解底层数据库的复杂性，就能高效地进行应用程序设计。在使用过程中，用户必须遵守Oracle的许可协议，该协议限制了软件的使用、复制和分发，并受知识产权法律保护。未经明确授权，用户不得对软件进行反向工程、拆解或重新编译，除非法律法规要求为了实现兼容性。同时，文档中的信息可能随时更新，且不保证无误，用户在发现错误时应向Oracle报告。本指南详细介绍了如何配置、安装、管理和维护Oracle Database Gateway，包括如何设置连接参数、处理事务、优化性能以及解决可能出现的问题。此外，它还提供了示例代码和实用技巧，帮助开发人员快速上手并有效地利用这个工具进行数据迁移、数据同步和数据访问。 Oracle Database Gateway for Informix是一个关键的技术组件，对于那些需要在Oracle和Informix数据库之间进行高效数据交互的企业和开发者来说，理解和掌握其使用方法是至关重要的。通过阅读这份用户指南，用户将能够充分利用这种跨平台的数据库集成能力，提升应用系统的灵活性和效率。

Informix Gateway Features and Restrictions 2-1

Informix Gateway Features and Restrictions

After the gateway is installed and configured, you can use the gateway to access

Informix data, pass Informix commands from applications to the Informix database,

perform distributed queries, and copy data.

This chapter contains the following sections:

■ Using the Pass-Through Feature

■ CHAR Semantics

■ Multi-byte Character Sets Ratio Suppression

■ IPv6 Support

■ Gateway Session IDLE Timeout

■ Database Compatibility Issues for Informix

■ Known Restrictions

■ Known Problems

Using the Pass-Through Feature

The gateway can pass Informix commands or statements from the application to the

Informix database using the DBMS_HS_PASSTHROUGH package.

Use the DBMS_HS_PASSTHROUGH package in a PL/SQL block to specify the statement

to be passed to the Informix database, as follows:

DECLARE

num_rows INTEGER;

BEGIN

num_rows := DBMS_HS_PASSTHROUGH.EXECUTE_IMMEDIATE@IFMX('command');

END;

Where command cannot be one of the following:

■ COMMIT

■ CREATE DATABASE

■ DROP DATABASE

■ ROLLBACK

■ ROLLFORWARD DATABASE

■ Informix tool commands

CHAR Semantics

2-2 Oracle Database Gateway for Informix User's Guide

The DBMS_HS_PASSTHROUGH package supports passing bind values and executing

SELECT statements.

CHAR Semantics

This feature allows the gateway to optionally run in CHAR Semantics mode. Rather

than always describing Informix CHAR columns as CHAR(n BYTE), this feature

describes them as CHAR(n CHAR) and VARCHAR(n CHAR). The concept is similar to

Oracle database CHAR Semantics. You need to specify HS_NLS_LENGTH_

SEMANTICS=CHAR gateway parameter to activate this option. Refer to Appendix D

for more detail.

Multi-byte Character Sets Ratio Suppression

This feature optionally suppresses the ratio expansion from Informix database to

Oracle database involving multi-byte character set. By default, Oracle gateways

assume the worst ratio to prevent data being truncated or insufficient buffer size

situation. However, if you have specific knowledge of your Informix database and do

not want the expansion to occur, you can specify HS_KEEP_REMOTE_COLUMN_SIZE

parameter to suppress the expansion. Refer toAppendix D for more detail.

IPv6 Support

Besides full IPv6 support between Oracle databases and the gateway, IPv6 is also

supported between this gateway and Informix database. Refer to the HS_FDS_

CONNECT_INFO parameter in Appendix D for more detail.

Gateway Session IDLE Timeout

You can optionally choose to terminate long idle gateway sessions automatically with

the gateway parameter HS_IDLE_TIMEOUT. Specifically, when a gateway session is

idle for more than the specified time limit, the gateway session is terminated with any

pending update rolled back. Refer to the HS_IDLE_TIMEOUT parameter in

Appendix D for more detail.

Database Compatibility Issues for Informix

Informix and Oracle databases function differently in some areas, causing

compatibility problems. The following compatibility issues are described in this

section:

■ ANSI SQL Standard

■ Naming Rules

■ Data Types

Note: It is recommended that you COMMIT after each DDL statement

in the pass-through.

See Also: Oracle Database PL/SQL Packages and Types Reference and

Chapter 3, Features of Oracle Database Gateways, of Oracle

Database Heterogeneous Connectivity User's Guide for more

information about the DBMS_HS_PASSTHROUGH package.

Database Compatibility Issues for Informix

2-4 Oracle Database Gateway for Informix User's Guide

If the Informix table called emp is owned by SCOTT, a table owner name in uppercase

letters, you can enter the owner name without double quote characters, as follows:

SQL> SELECT * FROM SCOTT."emp"@IFMX;

SQL> SELECT * FROM scott."emp"@IFMX;

Oracle recommends that you surround all Informix object names with double quote

characters and use the exact letter case for the object names as they appear in the

Informix data dictionary. This convention is not required when referring to the

supported Oracle data dictionary tables or views listed in Appendix C, "Data

Dictionary".

If existing applications cannot be changed according to these conventions, create views

in Oracle to associate Informix names to the correct letter case. For example, to refer to

the Informix table emp from an existing Oracle application by using only uppercase

names, define the following view:

SQL> CREATE VIEW EMP (EMPNO, ENAME, SAL, HIREDATE)

AS SELECT "empno", "ename", "sal", "hiredate"

FROM "emp"@IFMX;

With this view, the application can issue statements such as the following:

SQL> SELECT EMPNO, ENAME FROM EMP;

Using views is a workaround solution that duplicates data dictionary information

originating in the Informix data dictionary. You must be prepared to update the Oracle

view definitions whenever the data definitions for the corresponding tables are

changed in the Informix database.

Data Types

Data type issues include the following:

■ Binary, Byte and Text Literal Notation

■ Data Type Conversion

Binary, Byte and Text Literal Notation

Oracle SQL uses hexadecimal digits surrounded by single quotes to express literal

values being compared or inserted into columns defined as data type RAW.

This notation is not converted to syntax compatible with Informix BINARY, BYTE and

TEXT data types (a 0x followed by hexadecimal digits, surrounded by single quotes).

For example, the following statement is not supported:

SQL> INSERT INTO BYTE_TAB@IFMX VALUES (’Oxff’);

Where BYTE_TAB contains a column of data type BINARY, BYTE or TEXT. Use bind

variables when inserting into or updating BINARY, BYTE or TEXT data types.

Data Type Conversion

Informix does not support implicit date conversions. Such conversions must be

explicit.

For example, the gateway issues an error for the following SELECT statement:

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