11g Advanced Compression - How to Check Space Occupied by LOB Compression
(Doc ID 861344.1)
Last updated on JULY 05, 2023
Applies to:
Oracle Database Backup Service - Version N/A and laterOracle Database Exadata Express Cloud Service - Version N/A and later
Oracle Database Cloud Service - Version N/A and later
Oracle Database - Enterprise Edition - Version 11.1.0.6 and later
Oracle Database Cloud Schema Service - Version N/A and later
Information in this document applies to any platform.
Goal
This note shows how LOB columns can be compressed and storage savings can be gained by using Oracle 11g Advanced Compression features.
The example script calculates (1) space used, (2) space saved between an uncompressed LOB column and a compressed LOB column, and (3) space saved between a compressed LOB column and a compressed LOB column with the DEDUPLICATE option.
The below table shows space occupied by tables with different COMPRESS option after loading some data:
| BasicFile (no compress) | SecureFile (compress) | SecureFile (compress & deduplicate) | |
|---|---|---|---|
| Space Used in Bytes | 4423680 | 1236992 | 49152 |
| Space Used in Blocks | 540 | 151 | 6 |
NOTE:
Note that a table can be compressed without compressing LOB data as both are stored in different segments.
Please refer to:
Oracle® Database Concepts
11g Release 2 (11.2)
Part Number E25789-01
Chapter 2 Tables and Table Clusters
Section 'Table Compression'
Note that a table can be compressed without compressing LOB data as both are stored in different segments.
Please refer to:
Oracle® Database Concepts
11g Release 2 (11.2)
Part Number E25789-01
Chapter 2 Tables and Table Clusters
Section 'Table Compression'
Solution
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In this Document
| Goal |
| Solution |
| Scripts |
| Resulting Data: Space occupied using different COMPRESS options |
| References |