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About Oracle Large Objects (LOBs)

You can access the Oracle large object datatypes: binary large objects (BLOBs), character large objects (CLOBs), and binary files (BFILEs).

On an Oracle Database Server, these datatypes can store objects of up to 4 gigabytes in size. They are similar in purpose to the familiar Oracle7 LONG and LONG RAW datatypes, but offer a number of additional advantages.

Comparison of LOBs with LONGs

LOBs

LONGs

Up to 4 gigabytes

Up to 2 gigabytes

Multiple LOB columns allowed in a single table

Only one LONG column allowed per table

Replication supported

No replication

Random data access supported

Only sequential access supported

Better table space management (only LOB locator is stored)

Less efficient (data is stored directly in table)

Allowed in user-defined object types

Not allowed

Easily passed to procedures and external calls

Not easily passed

LOBs in detail:

BLOBs are used to store large objects in binary format. CLOBs are used to store character data. These two types are also known as internal LOBs, because their data is stored within the server. The data participates in transactions and integrity control, including commits and rollbacks.

BFILEs, in contrast, are stored outside of the server. The server stores only the operating system address of the file. As a consequence, BFILEs can not participate in database transactions.

Compatibility

Because of the various advantages offered by LOBs (see the table above), you should used LOBs instead of LONGs in any new application.

However, for backward compatibility, LONGs are still fully supported.

Forms Types

Within a form, the LOB would usually be given a control type of Text or Image, depending on its nature and usage.

Restrictions