可以使用 alter database datafile 'file path...' resize xM 的命令来缩小数据文件。
SELECT 'alter database datafile ''' || A.FILE_NAME || ''' resize ' ||
ROUND(A.FILESIZE - (A.FILESIZE - C.HWMSIZE - 100) * 0.8) || 'M;',
A.FILESIZE || 'M' AS "数据文件的总大小", C.HWMSIZE || 'M' AS "数据文件的实用大小"
FROM (SELECT FILE_ID, FILE_NAME, ROUND(BYTES / 1024 / 1024) AS FILESIZE
FROM DBA_DATA_FILES) A,
(SELECT FILE_ID, ROUND(MAX(BLOCK_ID) * 8 / 1024) AS HWMSIZE
FROM DBA_EXTENTS
GROUP BY FILE_ID) C
WHERE A.FILE_ID = C.FILE_ID AND
A.FILESIZE - C.HWMSIZE > 100;
or
SELECT 'alter database ' || A.NAME || ' datafile ''' || B.FILE_NAME || '''' ||
' resize ' ||
GREATEST(TRUNC(BYTES_FULL / .7), (BYTES_TOTAL - BYTES_FREE)) ||
CHR(10) || '--tablespace was ' ||
TRUNC(BYTES_FULL * 100 / BYTES_TOTAL) || '% full now ' ||
TRUNC(BYTES_FULL * 100 /
GREATEST(TRUNC(BYTES_FULL / .7), (BYTES_TOTAL - BYTES_FREE))) || '%'
FROM V$DATABASE A, DBA_DATA_FILES B,
(SELECT TABLESPACE_NAME, SUM(BYTES) BYTES_FULL
FROM DBA_EXTENTS
GROUP BY TABLESPACE_NAME) C,
(SELECT TABLESPACE_NAME, SUM(BYTES) BYTES_TOTAL
FROM DBA_DATA_FILES
GROUP BY TABLESPACE_NAME) D,
(SELECT A.TABLESPACE_NAME, A.FILE_ID, B.BYTES BYTES_FREE
FROM (SELECT TABLESPACE_NAME, FILE_ID,
MAX(BLOCK_ID) MAX_DATA_BLOCK_ID
FROM DBA_EXTENTS
GROUP BY TABLESPACE_NAME, FILE_ID) A, DBA_FREE_SPACE B
WHERE A.TABLESPACE_NAME = B.TABLESPACE_NAME AND
A.FILE_ID = B.FILE_ID AND
B.BLOCK_ID > A.MAX_DATA_BLOCK_ID) E
WHERE B.TABLESPACE_NAME = C.TABLESPACE_NAME AND
B.TABLESPACE_NAME = D.TABLESPACE_NAME AND
BYTES_FULL / BYTES_TOTAL < .7 AND
B.TABLESPACE_NAME = E.TABLESPACE_NAME AND
B.FILE_ID = E.FILE_ID;
alter tablespace TABLESPACENAME coalesce
此语句是整合表空间的碎片增加表空间的连续性，但是他不会收缩一个文件的大小的
选择某个表空间中超过N个blocks的segments，通过此语句可以看出那个表占用的空间大
SELECT OWNER, SEGMENT_NAME, SEGMENT_TYPE, BLOCKS
FROM DBA_SEGMENTS
WHERE TABLESPACE_NAME = 'RISK' AND
BLOCKS > 1000
ORDER BY BLOCKS DESC;
分析表，得知表的一些信息
analyze table TABLENAME estimate statistics;
SELECT INITIAL_EXTENT, NEXT_EXTENT, MIN_EXTENTS, BLOCKS, EMPTY_BLOCKS
FROM DBA_TABLES
WHERE TABLE_NAME = 'xx' AND
OWNER = 'xx';
用alter table ... deallocate unused命令回收表的空间
alter table user.tablename deallocate unused keep 1k;
)
