COMPRESSION_ALGORITHM

Default: BASIC

Purpose

Specifies the compression algorithm to be used when compressing dump file data.

Syntax and Description

COMPRESSION_ALGORITHM = {BASIC | LOW | MEDIUM | HIGH}

The parameter options are defined as follows:

  • BASIC--Offers a good combination of compression ratios and speed; the algorithm used is the same as in previous versions of Oracle Data Pump.

  • LOW---Least impact on export throughput and suited for environments where CPU resources are the limiting factor.

  • MEDIUM---Recommended for most environments. This option, like the BASIC option, provides a good combination of compression ratios and speed, but it uses a different algorithm than BASIC.

  • HIGH--Best suited for situations in which dump files will be copied over slower networks where the limiting factor is network speed.

The performance of a compression algorithm is characterized by its CPU usage and by the compression ratio (the size of the compressed output as a percentage of the uncompressed input). These measures vary on the size and type of inputs as well as the speed of the compression algorithms used. The compression ratio generally increases from low to high, with a trade-off of potentially consuming more CPU resources.

It is recommended that you run tests with the different compression levels on the data in your environment. Choosing a compression level based on your environment, workload characteristics, and size and type of data is the only way to ensure that the exported dump file set compression level meets your performance and storage requirements.

Restrictions

  • To use this feature, database compatibility must be set to 12.0.0 or later.

  • This feature requires that the Oracle Advanced Compression option be enabled.

Example 1

This example performs a schema-mode unload of the HR schema and compresses only the table data using a compression algorithm with a low level of compression. This should result in fewer CPU resources being used, at the expense of a less than optimal compression ratio.

       > expdp hr DIRECTORY=dpump_dir1 DUMPFILE=hr.dmp COMPRESSION=DATA_ONLY 
COMPRESSION_ALGORITHM=LOW

Example 2

This example performs a schema-mode unload of the HR schema and compresses both metadata and table data using the basic level of compression. Omitting the COMPRESSION_ALGORITHM parameter altogether is equivalent to specifying BASIC as the value.

       > expdp hr DIRECTORY=dpump_dir1 DUMPFILE=hr.dmp COMPRESSION=ALL COMPRESSION_ALGORITHM=BASIC