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Richard Niemiec

"Oracle Database 10g Performance Tuning Tips & Techniques"


DBA_FREE_SPACE
The view DBA_FREE_SPACE is broken down by datafile number within the tablespace. You can
easily compute the amount of free space in each tablespace by using the following query:
SQL> select tablespace_name, sum(bytes) from dba_free_space
2 group by tablespace_name;
TABLESPACE_NAME SUM(BYTES)
---------------- ----------
DMARTS 194969600
XPORT 180289536
SYSAUX 44105728
UNDOTBS1 75169792
USERS3 104792064
USERS4 260046848
USERS 1376256
USERS2 104792064
SYSTEM 75104256
EXAMPLE 23724032
10 rows selected.
Note that the free space does not take into account the space that would be available if and
when the datafiles in a tablespace are autoextended. Also, any space allocated to a table for rows
that are later deleted will be available for future inserts into the table, but it is not counted in the
preceding query results as space available for other database objects. When a table is truncated,
however, the space is made available for other database objects.
DBA_LMT_FREE_SPACE
The view DBA_LMT_FREE_SPACE provides the amount of free space, in blocks, for all tablespaces
that are locally managed, and it must be joined with DBA_DATA_FILES to get the tablespace names.
DBA_THRESHOLDS
New to Oracle 10g, DBA_THRESHOLDS contains the currently active list of the different metrics
that gauge the database??™s health and specify a condition under which an alert will be issued if the
metric threshold reaches or exceeds a specified value.


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