Identifying Tablespaces Needing More Space in Oracle Database

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.

Posts in this series