Preface

This Guide describes Oracle9i application development features that deal with Large Objects (LOBs). The information applies to all platforms, and does not include system-specific information.

This preface contains these topics:

Feature Coverage and Availability

Oracle9i Application Developer's Guide - Large Objects (LOBs) contains information that describes the features and functionality of Oracle9i and Oracle9i Enterprise Edition products. Oracle9i and Oracle9i Enterprise Edition have the same basic features; however, several advanced features are available only with the Enterprise Edition, and some of these are optional. To use the Partitioning functionality, select the Partitioning option.

Note:

From this release, in Oracle9i Enterprise Edition, you no longer need to select the Objects options to install the Objects and functionality.

What You Need To Use LOBs

Although there are no special system restrictions when dealing with LOBs:

See Also:

The following sections in Chapter 4, "Managing LOBs":

Audience

The Oracle9i Application Developer's Guide - Large Objects (LOBs) is intended for programmers developing new applications that use LOBs, as well as those who have already implemented this technology and now wish to take advantage of new features.

The increasing importance of multimedia data as well as unstructured data has led to this topic being presented as an independent volume within the Oracle Application Developers documentation set.

Organization

Oracle9i Application Developer's Guide - Large Objects (LOBs) contains thirteen chapters organized into two volumes. A brief summary of what you will find in each chapter follows:

Oracle9i Application Developer's Guide - Large Objects (LOBs) Volume 1

Chapter 1, "Introduction to LOBs"

Chapter 1 describes the need for unstructured data and the advantages of using LOBs. It discusses the use of LOBs to promote internationalization by way of CLOBS, and the advantages of using LOBs over LONGs. Chapter 1 also describes the LOB demo file and where to find the supplied LOB sample scripts.

Chapter 2, "Basic LOB Components"

Chapter 2 describes the LOB datatype, including internal persistent and temporary LOBs and external LOBs, (BFILEs). The need to initialize LOBs to NULL or Empty is described. The LOB locator and how to use it is also discussed.

Chapter 3, "LOB Support in Different Programmatic Environments"

Chapter 3 describes the eight programmatic environments used to operate on LOBs and includes a listing of their available LOB-related methods or procedures:

PL/SQL by means of the DBMS_LOB package as described in Oracle9i Supplied PL/SQL Packages and Types Reference.
C by means of Oracle Call Interface (OCI) described in the Oracle Call Interface Programmer's Guide
C++ by means of Oracle C++ Call Interface (OCCI) described in the Oracle C++ Call Interface Programmer's Guide
C/C++ by means of Pro*C/C++ precompiler as described in the Pro*C/C++ Precompiler Programmer's Guide
COBOL by means of Pro*COBOL precompiler as described in the Pro*COBOL Precompiler Programmer's Guide
Visual Basic by means of Oracle Objects For OLE (OO4O) as described in its accompanying online documentation.
Java by means of the JDBC Application Programmers Interface (API) as described in the Oracle9i JDBC Developer's Guide and Reference.
OLEDB by means of OraOLEDB, as described in the Oracle Provider for OLE DB User's Guide at http://otn.oracle.com/tech/nt/ole_db

Chapter 4, "Managing LOBs"

Chapter 4 describes how to use SQL*Loader, DBA actions required prior to working with LOBs, and LOB restrictions.

Chapter 5, "Large Objects: Advanced Topics"

Chapter 5 covers advanced topics that touch on all the other chapters. Specifically, it focuses on read consistent locators, the LOB buffering subsystem, LOBs in the object cache, and using Partitioned Index-Organized Tables with LOBs.

Chapter 6, "Frequently Asked Questions about LOBs"

Chapter 6 includes a list of LOB-related questions and answers received from users.

Chapter 7, "Modeling and Design"

Chapter 7 covers issues related to selecting a datatype and includes a comparison of LONG and LONG RAW properties. Table architecture design criteria are discussed and include tablespace and storage issues, reference versus copy semantics, index-organized tables, and partitioned tables. This chapter also describes using SQL semantics for LOBs, and indexing a LOB column.

Chapter 8, "Migrating From LONGs to LOBs"

This chapter describes what you need to know when migrating from LONGs to LOBs using the LONG API for LOBs. This API ensures that when you change your LONG columns to LOBs, your existing applications will require few changes, if any.

Chapter 9, "LOBS: Best Practices"

This chapter describes guidelines for using SQL*Loader to load LOBs, as well as LOB and temporary LOB performance guidelines.

Chapter 10, "Internal Persistent LOBs"

The basic operations concerning internal persistent LOBs are discussed, along with pertinent issues in the context of the scenario outlined in Chapter 9. We introduce the Unified Modeling Language (UML) notation with a special emphasis on use cases. Specifically, each basic operation is described as a use case. A full description of UML is beyond the scope of this book, but the small set of conventions used in this book appears later in the Preface. Wherever possible, we provide the same example in each programmatic environment.

Oracle9i Application Developer's Guide - Large Objects (LOBs) Volume 2

Chapter 11, "Temporary LOBs"

This chapter follows the same pattern as Chapter 10 but here focuses on temporary LOBs. New JDBC APIs in this release for Temporary LOBs include Creating a Temporary LOB, Checking if the BLOB/CLOB is temporary, and Freeing a Temporary BLOB/CLOB, comparing and trimming temporary LOBs. Visual Basic (OO4O) examples for temporary LOBs are not provided in this release but will be available in a future release.

Chapter 12, "External LOBs (BFILEs)"

This chapter focuses on external LOBs, also known as BFILEs. The same treatment is provided here as in Chapters 10 and 11, namely, every operation is treated as a use case, and you will find matching code examples in the available programmatic environments.

Chapter 13, "Using OraOLEDB to Manipulate LOBs"

This chapter describes how to manipulate LOBs using ADO Recordsets and OraOLEDB.

Chapter 14, "LOBs Case Studies"

This chapter describes how to build a multimedia repository using LOBs. It also includes some first steps to consider when building a LOB based Web site.

Appendix A, "Unified Modeling Language Diagrams"

This appendix explains how to use the Universal Modeling Language (UML) syntax used in the use case diagrams in Chapters 10, 11, and 12.

Appendix B, "The Multimedia Schema"

This provides a sample multimedia case study and solution. It includes the design of the multimedia application architecture in the form of table Multimedia_tab and associated objects, types, and references.

Conventions

This section describes the conventions used in the text and code examples of this documentation set. It describes:

Conventions in Text

We use various conventions in text to help you more quickly identify special terms. The following table describes those conventions and provides examples of their use.

Convention	Meaning	Example
Bold	Bold typeface indicates terms that are defined in the text or terms that appear in a glossary, or both.	When you specify this clause, you create an index-organized table.
Italics	Italic typeface indicates book titles or emphasis.	Oracle9i Database Concepts Ensure that the recovery catalog and target database do not reside on the same disk.
`UPPERCASE monospace (fixed-width font)`	Uppercase monospace typeface indicates elements supplied by the system. Such elements include parameters, privileges, datatypes, RMAN keywords, SQL keywords, SQL*Plus or utility commands, packages and methods, as well as system-supplied column names, database objects and structures, usernames, and roles.	You can specify this clause only for a `NUMBER` column. You can back up the database by using the `BACKUP` command. Query the `TABLE_NAME` column in the `USER_TABLES` data dictionary view. Use the `DBMS_STATS`.`GENERATE_STATS` procedure.
`lowercase monospace (fixed-width font)`	Lowercase monospace typeface indicates executables, filenames, directory names, and sample user-supplied elements. Such elements include computer and database names, net service names, and connect identifiers, as well as user-supplied database objects and structures, column names, packages and classes, usernames and roles, program units, and parameter values. Note: Some programmatic elements use a mixture of UPPERCASE and lowercase. Enter these elements as shown.	Enter `sqlplus` to open SQL*Plus. The password is specified in the `orapwd` file. Back up the datafiles and control files in the `/disk1/oracle/dbs` directory. The `department_id`, `department_name`, and `location_id` columns are in the `hr.departments` table. Set the `QUERY_REWRITE_ENABLED` initialization parameter to `true.` Connect as `oe` user. The `JRepUtil` class implements these methods.
`lowercase monospace (fixed-width font) italic`	Lowercase monospace italic font represents placeholders or variables.	You can specify the `parallel_clause`. Run `U``old_release``.SQL` where `old_release` refers to the release you installed prior to upgrading.

Conventions in Code Examples

Code examples illustrate SQL, PL/SQL, SQL*Plus, or other command-line statements. They are displayed in a monospace (fixed-width) font and separated from normal text as shown in this example:

SELECT username FROM dba_users WHERE username = 'MIGRATE';

The following table describes typographic conventions used in code examples and provides examples of their use.

Convention	Meaning	Example
[ ]	Brackets enclose one or more optional items. Do not enter the brackets.	`DECIMAL (``digits` `[ ,` `precision` `])`
{ }	Braces enclose two or more items, one of which is required. Do not enter the braces.	`{ENABLE \| DISABLE}`
\|	A vertical bar represents a choice of two or more options within brackets or braces. Enter one of the options. Do not enter the vertical bar.	`{ENABLE \| DISABLE}` `[COMPRESS \| NOCOMPRESS]`
`...`	Horizontal ellipsis points indicate either: That we have omitted parts of the code that are not directly related to the example That you can repeat a portion of the code	`CREATE TABLE ... AS` `subquery``;` `SELECT` `col1``,` `col2``, ... ,` `coln` `FROM employees;`
. . .	Vertical ellipsis points indicate that we have omitted several lines of code not directly related to the example.	SQL> SELECT NAME FROM V$DATAFILE; NAME ------------------------------------ /fsl/dbs/tbs_01.dbf /fs1/dbs/tbs_02.dbf . . . /fsl/dbs/tbs_09.dbf 9 rows selected.
Other notation	You must enter symbols other than brackets, braces, vertical bars, and ellipsis points as shown.	`acctbal NUMBER(11,2);` `acct CONSTANT NUMBER(4) := 3;`
`Italics`	Italicized text indicates placeholders or variables for which you must supply particular values.	`CONNECT SYSTEM/``system_password` `DB_NAME =` `database_name`
`UPPERCASE`	Uppercase typeface indicates elements supplied by the system. We show these terms in uppercase in order to distinguish them from terms you define. Unless terms appear in brackets, enter them in the order and with the spelling shown. However, because these terms are not case sensitive, you can enter them in lowercase.	`SELECT last_name, employee_id FROM employees;` `SELECT * FROM USER_TABLES;` `DROP TABLE hr.employees;`
`lowercase`	Lowercase typeface indicates programmatic elements that you supply. For example, lowercase indicates names of tables, columns, or files. Note: Some programmatic elements use a mixture of UPPERCASE and lowercase. Enter these elements as shown.	`SELECT last_name, employee_id FROM employees;` `sqlplus hr/hr` `CREATE USER mjones IDENTIFIED BY ty3MU9;`

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