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1. Free Space in a Tablespace Administration Tips
Finding the amount of used and free space in a Tablespace
The following bit of SQL will do the trick:
SELECT TABLESPACE_NAME,
ROUND(SUM(TOTAL_MB)-SUM(FREE_MB)) MB_USED,
ROUND(SUM(TOTAL_MB)) MB_SIZE,
ROUND((SUM(TOTAL_MB)-SUM(FREE_MB))/SUM(TOTAL_MB)*100) PCT_FULL,
ROUND(SUM(MAX_MB) - (SUM(TOTAL_MB)-SUM(FREE_MB))) MB_FREE,
ROUND(SUM(MAX_MB)) MB_MAXSIZE,
ROUND((SUM(TOTAL_MB)-SUM(FREE_MB))/SUM(MAX_MB)*100) PCT_UTIL
FROM
(SELECT TABLESPACE_NAME,SUM(BYTES)/1024/1024 FREE_MB,0 TOTAL_MB,0 MAX_MB
FROM DBA_FREE_SPACE GROUP BY TABLESPACE_NAME
UNION
SELECT TABLESPACE_NAME,0 CURRENT_MB,SUM(BYTES)/1024/1024 TOTAL_MB,
SUM(DECODE(MAXBYTES, 0, BYTES, MAXBYTES))/1024/1024 MAX_MB
FROM DBA_DATA_FILES GROUP BY TABLESPACE_NAME)
GROUP BY TABLESPACE_NAME;
You'll get a report that looks a bit like this:
TABLESPACE_NAME MB_USED MB_SIZE PCT_FULL MB_FREE MB_MAXSIZE PCT_UTIL
--------------- ---------- ---------- ---------- ---------- ---------- ----------
INDX 0 25 0 16384 16384 0
SYSTEM 87 325 27 16297 16384 1
UNDOTBS 1 200 1 16383 16384 0
USERS 0 25 0 16384 16384 0
The various columns can be explained thus:
MB_USED: Total amount of space currently in use within a tablespace
MB_SIZE: Total size of the tablespace, adding up the physical sizes of all datafiles
PCT_FULL: Used divided by Size, expressed as a percentage
MB_FREE: Total amount of tablespace still sitting there empty
MB_MAXSIZE: This shows how big the tablespace can become. Often this will be the same as the MB_SIZE
column -but not if you've switched on autoextend, in which case this column will show the
maxsize parameter
PCT_UTIL: Size divided by Maxsize expressed as a percentage
In other words, PCT_FULL shows you what percentage of what you've currently got is being
used, whereas PCT_UTIL shows what percentage of the maximum you could possibly *one
day* have is being used. Personally, I wouldn't touch autoextend with a barge pole, and I'd
be looking to resize or add extra datafiles when the PCT_FULL column is reaching around
the 75 - 80% mark.
Copyright © Howard Rogers 2001 10/17/2001 Page 1 of 1