SQL> analyze table scott.emp compute statistics;
Table analyzed.
SQL> select num_rows,AVG_ROW_LEN
from dba_tables
where table_name='EMP';
NUM_ROWS AVG_ROW_LEN
---------- -----------
14 40
SQL> SELECT table_name, initial_extent, next_extent,
max_extents, num_rows,pct_free
FROM dba_tables
WHERE table_name = 'EMP';
TABLE_NAME INITIAL_EXTENT NEXT_EXTENT MAX_EXTENTS NUM_ROWS PCT_FREE
--------------- -------------- ----------- ----------- ---------- -------------------------------------------------------------------------------
EMP 65536 2147483645 14 10
SQL> SELECT BYTES
FROM DBA_SEGMENTS
WHERE SEGMENT_NAME='EMP';
BYTES
----------
65536
SQL> ALTER TABLE SCOTT.EMP ALLOCATE EXTENT;
Table altered.
SQL> analyze table scott.emp compute statistics;
Table analyzed.
SQL> SELECT BYTES
FROM DBA_SEGMENTS
WHERE SEGMENT_NAME='EMP';
BYTES
----------
131072
SQL> ALTER TABLE SCOTT.EMP DEALLOCATE UNUSED;
Table altered.
SQL> SELECT BYTES
FROM DBA_SEGMENTS
WHERE SEGMENT_NAME='EMP';
BYTES
----------
65536