Oracle数据库空间回收从诊断到优化实战指南详细教程

SELECT TABLESPACE_NAME, FILE_NAME, 
       BYTES/1024/1024 AS SIZE_MB,
       (BYTES - (SELECT SUM(BYTES) 
        FROM DBA_FREE_SPACE 
        WHERE FILE_ID = df.FILE_ID))/1024/1024 AS USED_MB
FROM DBA_DATA_FILES df
ORDER BY SIZE_MB DESC;

SELECT table_name, blocks, empty_blocks, num_rows
FROM user_tables
WHERE table_name = 'YOUR_TABLE';

-- SHRINK方案（适用于ASSM表空间）
ALTER TABLE sales ENABLE ROW MOVEMENT;
ALTER TABLE sales SHRINK SPACE CASCADE; 
-- MOVE方案（通用性最强）
ALTER TABLE orders MOVE TABLESPACE users NOLOGGING PARALLEL 4;
ALTER INDEX orders_pk REBUILD PARALLEL 4;
-- 在线表重定义（最大程度保证业务连续性）
EXEC DBMS_REDEFINITION.START_REDEF_TABLE('SCHEMA','ORDERS','ORDERS_NEW');

ALTER DATABASE DATAFILE '/oradata/users01.dbf' RESIZE 1024M;

CREATE TABLESPACE app_data 
  DATAFILE '/oradata/app01.dbf' SIZE 100M 
  AUTOEXTEND ON NEXT 10M MAXSIZE 1G;

ALTER TABLE historical_data COMPRESS FOR OLTP;

-- 自动收缩表空间脚本
BEGIN
  FOR rec IN (SELECT file_id, file_name, bytes/1024/1024 current_size
              FROM dba_data_files 
              WHERE tablespace_name='USERS'
              AND autoextensible='NO')
  LOOP
    -- 计算新尺寸（保留10%缓冲）
    EXECUTE IMMEDIATE 'ALTER DATABASE DATAFILE '''||rec.file_name||''' RESIZE '||
                      (rec.current_size * 0.9) ||'M';
    DBMS_OUTPUT.PUT_LINE('Resized: '||rec.file_name);
  END LOOP;
END;

-- 表空间使用率监控
SELECT tablespace_name, 
       ROUND(1 - (free_space / total_space), 2) * 100 AS used_pct
FROM (
  SELECT tablespace_name,
         SUM(bytes) total_space,
         SUM(NVL(bytes_free,0)) free_space
  FROM dba_free_space 
  GROUP BY tablespace_name
) WHERE used_pct > 85; -- 设置85%阈值告警

-- 月度空间分析报告
SELECT owner, segment_name, segment_type,
       ROUND(bytes/1024/1024,2) size_mb
FROM dba_segments 
WHERE tablespace_name = 'USERS'
ORDER BY bytes DESC
FETCH FIRST 10 ROWS ONLY;