Representing Searchable Text Data

Rather than writing low-level code to do full-text searches, you can use Oracle9i Text, formerly known as ConText and interMedia Text. It stores the search data in a special kind of index, and lets you query the data with operators and PL/SQL packages. This makes it simple to create your own search engine using data from tables, files, or URLs, and combine the search logic with relational queries. You can also search XML data this way, using XPath notation.

For more information, see Oracle Text Application Developer's Guide.

Representing Large Amounts of Data

The database provides several datatypes for representing large amounts of data. These datatypes are grouped under the general category of Large Objects (LOBs); they are described in Table 2–6:

Table 2–6 Large Object Datatypes

Datatype Description

BLOB	Binary Large Object
	Suitable for representing large amounts of binary data such as
	images, video, or other multimedia data.
CLOB	Character Large Object
	Suitable for representing large amounts of character data. CLOB
	types are stored using the database character set.
NCLOB	National Character Set Large Object
	Suitable for representing large amounts of character data in
	National Character Set format.
BFILE	Datatype for storing Large Objects in the operating system's file
	system, outside of the database files or tablespace. Note that the
	BFILE type is read-only; other LOB types are read/write. BFILE
	objects are also sometimes referred to as external LOBs.

An instance of type BLOB, CLOB, or NCLOB can exist as either a persistent LOB instance or a temporary LOB instance. Persistent and temporary instances differ as follows:

■

A temporary LOB instance is declared in the scope of your application.

A persistent LOB instance is created and stored in the database.

2-34 Oracle Database Application Developer's Guide - Fundamentals

Representing Large Amounts of Data

With the exception of declaring, freeing, creating, and committing, operations on persistent and temporary LOB instances are performed the same way.

For more details on using LOBs in applications, see the Oracle Database Application Developer's Guide - Large Objects.

Note: In earlier releases, the LONG, RAW, and LONG RAW datatypes were typically used to store large amounts of data. Use of these types is no longer recommended for new development. If your application still uses these types, migrate your application to use LOB types. See the Oracle Database Application Developer's Guide - Large Objects

Using RAW and LONG RAW Datatypes

Note: Oracle recommends that you convert LONG RAW columns to binary LOB (BLOB) columns and convert LONG columns to character LOB (CLOB or NCLOB) columns. LOB columns are subject to far fewer restrictions than LONG and LONG RAW columns.