Identifying Top 10 Largest Database Segments in Oracle

Show the ten largest oracle objects in the database

SQL Code

 1col	owner format a15
 2col	segment_name format a30
 3col	segment_type format a15
 4col	mb format 999,999,999
 5select  owner
 6,	segment_name
 7,	segment_type
 8,	mb
 9from	(
10	select	owner
11	,	segment_name
12	,	segment_type
13	,	bytes / 1024 / 1024 "MB"
14	from	dba_segments
15	order	by bytes desc
16	)
17where	rownum < 11

Sample Oracle Output:

 1OWNER           SEGMENT_NAME                   SEGMENT_TYPE              MB
 2--------------- ------------------------------ --------------- ------------
 3MYAPP           TRANS_LOG                      TABLE                  7,880
 4MYAPP           DESCRIPTION                    INDEX                  6,028
 5MYAPP           EVT_LOG                        TABLE                  4,984
 6ARCHIVE         EVT_LOG                        TABLE                  3,080
 7MYAPP           ATTRIBUTES                     TABLE                  2,312
 8MYAPP           UNIQUE_EVT                     INDEX                  2,129
 9MYAPP           EVT_HOSTNAME                   INDEX                  1,409
10MYAPP           SOURCE                         INDEX                  1,407
128 rows selected.


  • To identify and display the 10 largest database segments by size, providing insights into space usage patterns and potential areas for optimization. This aids in database administration tasks such as space management, capacity planning, and performance tuning.


Formatting Output:

*   `col owner format a15`, `col segment_name format a30`, `col segment_type format a15`, `col mb format 999,999,999`: Adjusts column widths for readability and large numbers.

Retrieving and Ordering Segment Data:

*   `(select owner, segment_name, segment_type, bytes / 1024 / 1024 "MB" from dba_segments order by bytes desc)`:
    *   Queries the `dba_segments` view, which stores information about database segments.
    *   Selects relevant columns: owner, segment name, segment type, and size in megabytes.
    *   Orders results by size in descending order, highlighting the largest segments first.

Limiting Results:

*   `where rownum < 11`: Filters the results to show only the top 10 largest segments, providing a focused view of major space consumers.

Displaying Final Output:

*   Presents the following information for the top 10 segments:
    *   `owner`: Database user who owns the segment.
    *   `segment_name`: Name of the segment.
    *   `segment_type`: Type of segment (e.g., table, index, lob).
    *   `mb`: Size of the segment in megabytes.

Key Points:

  • Focus on Largest Segments: Identifies potential space hogs or areas for optimization.
  • Key Information: Provides essential details for understanding segment usage and ownership.
  • User-Centric View: Presents data in a clear and understandable format for database administrators.

Insights and Explanations:

  • Space Management:

    • Helps identify segments that might require attention for space-saving strategies, such as compression, archiving, or partitioning.
    • Guides storage allocation decisions and capacity planning.
  • Performance Tuning:

    • Large segments can impact performance, so understanding their characteristics can aid in optimization efforts.
  • Troubleshooting:

    • Can be used to investigate space-related issues, such as unexpected growth or storage constraints.
  • Customization:

    • Can be modified to filter for specific segment types or owners based on analysis needs.
  • Integration: Consider incorporating this code into regular database monitoring and reporting processes for proactive space management.

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