Large object data type (Large Object Data Types, LOB) for storing text, images, video, sound and other information. oracle predefined four large object type: BFILE, BLOB, CLOB, NCLOB
LOB locators LOB data pointer.
Typically, LOB data retrieved by operation or DBMS_LOB package.
LOB data and normal data is typically stored separately from the table can be placed in different spaces.
create table lob_test(
bf bfile,
b1 blob,
c1 clob,
nc1 nclob
)
lob(c1) store as (tablespace users)
lob(b1) store as (tablespace myspace);
BFILE is stored in the file pointer that points to operating system files, and BFILE is read-only, it can not be modified. Oracle DBA must ensure that the operating system files have permission to read BFILE points. BFILE not involved in the transaction database can not rollback or commit.
BLOB unstructured for storing binary data, up to 128TB, data is stored in a separate table space.
CLOB storage database character set format of character data, up to 128TB, the data stored in the table space.
CLOB NCLOB with the same function, but NCLOB used to store Unicode national character set data.