SQL> set linesize 200
SQL> select segment_name, sum(bytes / 1024 / 1024/1024)
from dba_segments
where segment_name='T_PM_DEBIT_CARD'
group by segment_name; 2 3 4
SEGMENT_NAME SUM(BYTES/1024/1024/1024)
--------------------------------------------------------------------------------- -------------------------
T_PM_DEBIT_CARD 16.1968994
truncate table T_PM_DEBIT_CARD;
SQL> select segment_name, sum(bytes / 1024 / 1024 / 1024)
from dba_segments
where segment_name = 'T_PM_DEBIT_CARD'
group by segment_name; 2 3 4
SEGMENT_NAME SUM(BYTES/1024/1024/1024)
--------------------------------------------------------------------------------- -------------------------
T_PM_DEBIT_CARD .836181641
为什么还有800M呢？
SQL> alter table T_PM_DEBIT_CARD deallocate unused keep 0;
Table altered.
SQL> select segment_name, sum(bytes / 1024 / 1024 / 1024)
from dba_segments
where segment_name = 'T_PM_DEBIT_CARD'
group by segment_name; 2 3 4
SEGMENT_NAME SUM(BYTES/1024/1024/1024)
--------------------------------------------------------------------------------- -------------------------
T_PM_DEBIT_CARD .051513672
是因为initial 分配的缘故.