Identifying Tablespaces Needing More Space in Oracle Database

calendar Feb 6, 2024 · 3 min read · database administration resource optimization performance monitoring data management tablespace datafiles dba_data_files dba_tablespaces  ·
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Description of Oracle Database SQL code for Identifying Tablespaces Needing Space

This code helps identify tablespaces requiring additional space to maintain an 80% utilization threshold in your Oracle database. Below is a breakdown of its purpose, components, and key points:

Sample SQL Command

 1set pages 999 lines 100
 2col	"Tablespace"	for a50
 3col	"Size MB" 	for 999999999
 4col	"%Used" 	for 999
 5col	"Add (80%)" 	for 999999
 6select	tsu.tablespace_name "Tablespace"
 7,	ceil(tsu.used_mb) "Size MB"
 8,	100 - floor(tsf.free_mb/tsu.used_mb*100) "%Used"
 9,	ceil((tsu.used_mb - tsf.free_mb) / .8) - tsu.used_mb "Add (80%)"
10from	(select tablespace_name, sum(bytes)/1024/1024 used_mb
11	from    dba_data_files group by tablespace_name) tsu
12,		(select ts.tablespace_name
13	,       nvl(sum(bytes)/1024/1024, 0) free_mb
14	from    dba_tablespaces ts, dba_free_space fs
15	where   ts.tablespace_name = fs.tablespace_name (+)
16	group by ts.tablespace_name) tsf
17where	tsu.tablespace_name = tsf.tablespace_name (+)
18and	100 - floor(tsf.free_mb/tsu.used_mb*100) >= 80
19order	by 3,4
20/

Sample Oracle Output:

 1SQL> set pages 999 lines 100
 2col     "Tablespace"    for a50
 3col     "Size MB"       for 999999999
 4col     "%Used"         fSQL> SQL> SQL> or 999
 5col     "Add (80%)"     for 999999
 6select  tsu.tablespace_name "Tablespace"
 7,       ceil(tsu.used_mb) "Size MB"
 8,       100 - floor(tsf.free_mb/tsu.used_mb*100) "%Used"
 9,       ceil((tsu.used_mb - tsf.free_mb) / .8) - tsu.used_mb "Add (80%)"
10from    (select tablespace_name, sum(bytes)/1024/1024 used_mb
11        from    dba_data_files group by tablespace_name) tsu
12,               (select ts.tablespace_name
13        ,       nvl(sum(bytes)/1024/1024, 0) free_mb
14        from    dba_tablespaces ts, dba_free_space fs
15        where   ts.tablespace_name = fs.SQL> SQL>   2    3    4    5    6    7    8    9   10  tablespace_name (+)
16        group by ts.tablespace_name) tsf
17where   tsu.tablespace 11   12  _name = tsf.tablespace_name (+)
18and     100 - floor(tsf.free_mb/tsu.used_mb*100) >= 80
19order   by 3,4
20/
21 13   14   15
22Tablespace                                            Size MB %Used Add (80%)
23-------------------------------------------------- ---------- ----- ---------
24SYSAUX                                                    730    95       130
25SYSTEM                                                   1070   100       260
26
27SQL>

Purpose:

  • Identify tablespaces exceeding 80% utilization.
  • Calculate the additional space needed to bring them back down to 80%.

Breakdown:

  • Set statements:
    • set pages 999: Increases displayed rows for better visibility.
    • set lines 100: Allows for potentially many results.
  • Column formatting: Customizes column widths and displays for clarity.
  • Selects:
    • tsu: Calculates total used space in MB per tablespace from dba_data_files.
    • tsf: Calculates available free space in MB per tablespace, handling null values with nvl(sum(bytes), 0). Joins with dba_tablespaces and dba_free_space.
  • Filtering and calculations:
    • where: Includes only tablespaces over 80% used (100 - %Used >= 80).
    • "Add (80%)": Calculates the space needed to reach 80% by:
      • Subtracting available free space from used space.
      • Dividing by 0.8 (100% - desired 80% utilization).
      • Subtracting used space again to get the net additional space needed.

Key points:

  • This code assumes a desired 80% utilization threshold. Adjust the filter condition based on your specific needs.
  • The calculated additional space reflects raw datafile size, not necessarily usable table space.
  • Consider factors like future growth estimates and performance implications before adding space.

Insights and explanations:

  • Monitoring tablespace utilization is crucial for preventing performance bottlenecks and ensuring efficient storage allocation.
  • Proactively managing space helps avoid sudden outages due to full tablespaces.
  • This code provides a starting point for identifying critical tablespaces. Analyze specific use cases and consult database administrators for informed decisions.

Additional notes:

  • Explore advanced tools like Automatic Storage Management (ASM) for more sophisticated storage management.
  • Always test and understand the impact of space alterations before implementing them in production environments.

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