Listing Objects in an Oracle Tablespace

Mon, 05 Feb 2024 00:00:00 +0000

SQL lists every segment within a specific tablespace in an Oracle database

A detailed explanation of Oracle Database SQL code used to list objects within a tablespace, including purpose, breakdown, key points, and insights.

Sample SQL Command

 1set pages 999
 2col owner format a15
 3col segment_name format a40
 4col segment_type format a20
 5select owner
 6, segment_name
 7, segment_type
 8from dba_segments
 9where lower(tablespace_name) like lower('%&tablespace%')
10order by owner, segment_name
11/

Sample Oracle Output

 1OWNER SEGMENT_NAME SEGMENT_TYPE
 2--------------- ---------------------------------------- --------------------
 3LARRY BIN$Q+k4qsgBLNngRAAQg5ZRWg==$0 INDEX
 4LARRY BIN$Q+k4qsgCLNngRAAQg5ZRWg==$0 TABLE
 5LARRY BIN$Q+k4qsgELNngRAAQg5ZRWg==$0 INDEX
 6LARRY BIN$Q+k4qsgFLNngRAAQg5ZRWg==$0 TABLE
 7LARRY BOX TABLE
 8LARRY BOX_PK INDEX
 9LARRY CD TABLE
10LARRY CD_PK INDEX
11LARRY LOCATION TABLE
12LARRY LOCATION_PK INDEX
13LARRY LOTS_OF_ROWS TABLE
14LARRY POO TABLE
15LARRY SERVERS TABLE
16LARRY SYS_C0023466 INDEX
17LARRY SYS_C0023467 INDEX
18LARRY SYS_C0027234 INDEX
19LARRY TEST_TABLE TABLE
20LARRY TRACK TABLE
21LARRY TRACK_PK INDEX
22
2319 rows selected.

Purpose

To identify and display every segment (tables, indexes, partitions and LOBs that have storage allocated) residing in a chosen tablespace.

Breakdown

set pages 999: This setting sets the number of lines on each page of output to 999, so column headings repeat less often if the tablespace holds a large number of objects.
col owner format a15, col segment_name format a40**, col segment_type format a20**: These lines define column formatting in the output. They set specific widths for the "owner", "segment_name", and "segment_type" columns to improve readability.
select owner, segment_name, segment_type: This clause selects three specific columns from the dba_segments system view:
- owner: The schema (user) who owns the object.
- segment_name: The actual name of the object.
- segment_type: The type of segment (TABLE, INDEX, TABLE PARTITION, INDEX PARTITION, LOBSEGMENT, etc.).
from dba_segments: This specifies the data source for the query. dba_segments holds information about all database segments, including their type, owner, and tablespace association.
where lower(tablespace_name) like lower('%&tablespace%'): This clause filters the results based on the tablespace name.
- lower(tablespace_name): Converts the tablespace name to lowercase for case-insensitive comparison.
- like lower('%&tablespace%'): Uses a wildcard comparison with % to accept any tablespace name passed as the &tablespace variable.
order by owner, segment_name: This clause sorts the output first by owner and then by segment name within each owner.

Key Points

This code relies on the dba_segments system view, which requires appropriate privileges to access (typically DBA or SYSDBA).
The like clause with wildcards allows for listing objects in any tablespace whose name matches the provided part.
The code filters for all object types (segment_type). If you only need specific types (e.g., tables), modify the where clause accordingly.
Consider additional filtering using other columns from dba_segments for more granular results.
Empty tables created with deferred segment creation (the default, DEFERRED_SEGMENT_CREATION = TRUE) have no segment until the first row is inserted, so they do not appear. Query dba_tables or dba_indexes by tablespace_name to catch them.

Insights and Explanations

set pages only controls how many lines SQL*Plus prints on each page, and so how often it repeats column headings; it has no effect on query cost. Use set pages 0 to suppress headings entirely when spooling to a file.
Because the filter uses '%name%', a partial name can match more than one tablespace (for example, USERS also matches USERS2). Enter the full tablespace name when you want only one.
The code provides a basic listing of segments. To show size, add bytes or blocks from dba_segments. dba_segments has no creation-date column; for the object creation date, join to dba_objects (column created) on owner and object_name = segment_name.

The query lists every segment within a specified tablespace. Empty tables with deferred segment creation are the main gap, so adapt it to your needs.

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