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Oracle Tips by Burleson |
Oracle 10g Data Pump Utilities
Data Pump is a new utility in Oracle 10g that
enables very high-speed metadata and data loading and unloading from
one database to another. The Data Pump Export and Import utilities
are restartable and (expdp and impdp) have a similar look and feel
to the original Export and Import utilities (exp and imp). However,
they use a new mechanism that provides a dramatic increase in
performance. as well as new features and functions.
Data
Pump Overview
The Oracle Data Pump utility – API is
implemented through a PL/SQL package (dbms_datapump). The Data Pump
makes use of the direct path load and the external table mechanisms
for data movement.
General Architecture
The Major functional components of Data Pump
are as follows:
dbms_datapump: This package embodies the
API for high-speed export and import utilities for bulk data and
metadata movement.
direct path api: This supports a stream
interface in addition to its existing column array interface. Row
data is read or written to dump file sets as a Direct Path API
stream. The Direct Path API also minimizes data conversion and
parsing at both unload and load time.
dbms_metadata: This package is used by
worker process for all metadata (database object definitions)
loading and unloading. The metadata is extracted and written to the
dump file set as XML documents rather than as SQL Data Definition
Language (DDL) in the original export utility. The XML format
brings great flexibility when creating the DDL during import time.
For example, you can easily change an object’s ownership and default
tablespace during an import operation. However, the XML format
takes up more dump file space than DDL.
External Table API: The Data Pump uses
Direct Path API to load and unload when a table’s structure allows
it. However, when Direct Path API cannot be used, the Data Pump
uses External Table API to move data. Oracle External Table API
has two access drivers. The oracle_loader access driver provides
external tables read-only access to SQL Loader compatible files.
And the oracle_datapump driver provides external tables write and
read access to data file set.
The Direct Path API is much faster than the
External Table API. However, Direct Path does not support the
following structures for loading and unloading data:
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Partitioned tables on which global index
exists during a single-partition load.
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LOB column for which
domain index exists.
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Clustered tables.
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Tables with active triggers
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