Oracle常用的诊断语句

--1.数据池命中率
--db_pool命中率(要求：95%左右)：
select 100 -
       100 * ((select value from v$sysstat where name = ‘physical reads‘)) /
       ((select value from v$sysstat where name = ‘consistent gets‘) +
       (select value from v$sysstat where name = ‘db block gets‘))
  from dual;

select *
  from V$PARAMETER
 where name in (‘sga_max_size‘,
                ‘db_cache_size‘,
                ‘shared_pool_size‘,
                ‘pga_aggregate_target‘);

--2.查找前十条性能差的sql(磁盘读取较大，缺少索引或语句不合理)
SELECT *
  FROM (SELECT PARSING_USER_ID EXECUTIONS,
               SORTS,
               COMMAND_TYPE,
               DISK_READS,
               sql_text
          FROM v$sqlarea
         ORDER BY disk_reads DESC)
 WHERE ROWNUM < 10;

SELECT sql_text, hash_value, executions, buffer_gets, disk_reads, parse_calls
 FROM V$SQLAREA
WHERE buffer_gets > 10000000 OR disk_reads > 1000000
ORDER BY buffer_gets + 100 * disk_reads DESC; 

--3.根据unix上Top命令看到的PID,查找对应的SQl
SELECT P.pid pid,
       S.sid sid,
       P.spid spid,
       S.username username,
       S.osuser osname,
       P.serial# S_#,
       P.terminal,
       P.program program,
       P.background,
       S.status,
       RTRIM(SUBSTR(a.sql_text, 1, 80)) SQL
  FROM v$process P, v$session S, v$sqlarea A
 WHERE P.addr = s.paddr
   AND S.sql_address = a.address(+)
   AND P.spid LIKE ‘%CPU最高的进程对应的PID%‘;

--4.察看IO情况：
select
    df.name 文件名,
    fs.phyrds 读次数,
    fs.phywrts 写次数,
    (fs.readtim/decode(fs.phyrds,0,-1,fs.phyrds)) 读时间,
    (fs.writetim/decode(fs.phywrts,0,-1,fs.phywrts)) 写时间
from  v$datafile df,
    v$filestat fs
where df.file#=fs.file#
order by df.name;

--5.表空间察看
SELECT UPPER(F.TABLESPACE_NAME) "表空间名",
       D.TOT_GROOTTE_MB "表空间大小(M)",
       D.TOT_GROOTTE_MB - F.TOTAL_BYTES "已使用空间(M)",
       TO_CHAR(ROUND((D.TOT_GROOTTE_MB - F.TOTAL_BYTES) / D.TOT_GROOTTE_MB * 100, 2), ‘990.99‘) "使用比",
       F.TOTAL_BYTES "空闲空间(M)",
       F.MAX_BYTES "最大块(M)"
FROM (SELECT TABLESPACE_NAME,
        ROUND(SUM(BYTES) / (1024 * 1024), 2) TOTAL_BYTES,
        ROUND(MAX(BYTES) / (1024 * 1024), 2) MAX_BYTES
    FROM SYS.DBA_FREE_SPACE GROUP BY TABLESPACE_NAME) F,
       (SELECT DD.TABLESPACE_NAME,ROUND(SUM(DD.BYTES) / (1024 * 1024), 2) TOT_GROOTTE_MB FROM SYS.DBA_DATA_FILES DD
 GROUP BY DD.TABLESPACE_NAME) D WHERE D.TABLESPACE_NAME = F.TABLESPACE_NAME
ORDER BY 4 DESC;

-- 数据表总行数排序
select   t.table_name, t.num_rows, t.*
from     user_tables t
where t.num_rows > 0
order by t.num_rows desc

-- 普通表数据大小排序
select segment_name,  trunc(bytes/1024/1024)
from user_segments
where segment_type = ‘TABLE‘
order by bytes desc;

-- 含LOB类型表的数据大小
SELECT A.TABLE_NAME,
       A.COLUMN_NAME,
       trunc(B.BYTES / 1024 / 1024),
       B.SEGMENT_NAME,
       B.SEGMENT_TYPE,
       B.TABLESPACE_NAME,
       B.BLOCKS,
       B.EXTENTS
  FROM USER_LOBS A, USER_SEGMENTS B
WHERE A.SEGMENT_NAME = B.SEGMENT_NAME
ORDER BY B.BYTES DESC;

-- 数据表总的数据大小占用
select  rowSize + nvl(lobSize, 0) dataSize, t1.*, t2.*
from (
          select segment_name,  trunc(bytes/1024/1024) rowSize
          from user_segments
          where segment_type = ‘TABLE‘
    ) t1 left join (   

          SELECT A.TABLE_NAME,
                 A.COLUMN_NAME,
                 trunc(B.BYTES / 1024 / 1024) lobSize,
                 B.SEGMENT_NAME,
                 B.SEGMENT_TYPE,
                 B.TABLESPACE_NAME,
                 B.BLOCKS,
                 B.EXTENTS
            FROM USER_LOBS A, USER_SEGMENTS B
          WHERE A.SEGMENT_NAME = B.SEGMENT_NAME
    ) t2 on t1.segment_name = t2.table_name
order by rowSize + nvl(lobSize, 0) desc

--6.运行时间很长的SQL
select username,
       sid,
       opname,
       round(sofar * 100 / totalwork, 0) || ‘%‘ as progress,
       time_remaining,
       sql_text
  from v$session_longops, v$sql
 where time_remaining <> 0
   and sql_address = address
   and sql_hash_value = hash_value;

--7.锁相关的查询
select ‘kill -9 ‘||PS.SPID,
‘alter system kill session ‘‘‘||vs.sid||‘,‘||vs.serial#||‘‘‘;‘,
/*       DECODE(V$LOCK.TYPE, ‘TM‘, ‘TABLE LOCK‘, ‘TX‘, ‘ROW LOCK‘, NULL) LOCK_LEVEL,*/
       Decode(VL.LOCKED_MODE,0,‘[0] none‘,
                      1,‘[1] null 空‘,
                      2,‘[2] Row-S 行共用(RS)：共用表鎖，sub share ‘,
                      3,‘[3] Row-X 行獨佔(RX)：用於行的修改，sub exclusive ‘,
                      4,‘[4] Share 共用鎖(S)：阻止其他DML操作，share‘,
                      5,‘[5] S/Row-X 共用行獨佔(SRX)：阻止其他事務操作，share/sub exclusive ‘,
                      6,‘[6] exclusive 獨佔(X)：獨立訪問使用，exclusive ‘,
                      ‘[‘||VL.LOCKED_MODE||‘] Other Lock‘) LockMode,
PS.SPID,OS_USER_NAME,VS.PROGRAM,VS.MACHINE,ORACLE_USERNAME,OBJECT_NAME,vs.LOGON_TIME ,
Vs.status,vs.MODULE
from  V$LOCKED_OBJECT VL ,DBA_OBJECTS OB ,V$SESSION VS ,v$process PS
WHERE VL.OBJECT_ID = OB.OBJECT_ID
AND   VL.SESSION_ID = VS.SID
AND   Ps.ADDR = Vs.PADDR

select ‘kill -9 ‘||PS.SPID,
‘alter system kill session ‘‘‘||vs.sid||‘,‘||vs.serial#||‘‘‘;‘,
/*       DECODE(V$LOCK.TYPE, ‘TM‘, ‘TABLE LOCK‘, ‘TX‘, ‘ROW LOCK‘, NULL) LOCK_LEVEL,*/
       Decode(VL.LOCKED_MODE,0,‘[0] none‘,
                      1,‘[1] null 空‘,
                      2,‘[2] Row-S 行共用(RS)：共用表鎖，sub share ‘,
                      3,‘[3] Row-X 行獨佔(RX)：用於行的修改，sub exclusive ‘,
                      4,‘[4] Share 共用鎖(S)：阻止其他DML操作，share‘,
                      5,‘[5] S/Row-X 共用行獨佔(SRX)：阻止其他事務操作，share/sub exclusive ‘,
                      6,‘[6] exclusive 獨佔(X)：獨立訪問使用，exclusive ‘,
                      ‘[‘||VL.LOCKED_MODE||‘] Other Lock‘) LockMode,
       PS.SPID,OS_USER_NAME,VS.PROGRAM,VS.MACHINE,ORACLE_USERNAME,OBJECT_NAME,vs.LOGON_TIME ,
       Vs.status,vs.MODULE, vs.SQL_ID, st.SQL_TEXT
from  V$LOCKED_OBJECT VL ,DBA_OBJECTS OB ,V$SESSION VS ,v$process PS, v$sqlarea st
WHERE VL.OBJECT_ID = OB.OBJECT_ID
      AND VL.SESSION_ID = VS.SID
      AND Ps.ADDR = Vs.PADDR
      and vs.SQL_ID = st.SQL_ID
      AND VS.USERNAME = ‘LC019999‘

select    st.SQL_FULLTEXT, vs.*
from      v$session vs
     join v$sql st on vs.SQL_ID = st.SQL_ID
where     vs.USERNAME = ‘scott‘
      and st.SQL_TEXT like ‘%%‘

--8.产生kill会话的Sql语句
select A.SID,
       B.SPID,
       A.SERIAL#,
       a.lockwait,
       A.USERNAME,
       A.OSUSER,
       a.logon_time,
       a.last_call_et / 3600 LAST_HOUR,
       A.STATUS,
       ‘orakill ‘ || sid || ‘ ‘ || spid HOST_COMMAND,
       ‘alter system kill session ‘‘‘ || A.sid || ‘,‘ || A.SERIAL# || ‘‘‘‘ SQL_COMMAND
  from v$session A, V$PROCESS B
 where A.PADDR = B.ADDR
   AND SID > 6;

-- 最近10分钟最消耗CPU的SQL语句：
select sql_text
from (
        select sql_id,count(*) as cn
        from v$active_session_history
        where sample_time > sysdate - 10/24/60
            and session_type <> ‘BACKGROUND‘
            and SESSION_STATE = ‘ON CPU‘
        group by sql_id
        order by cn desc
    ) ash, v$sql s
where ash.sql_id=s.sql_id;

-- 最近10分钟最消耗IO的SQL语句：
select sql_text
from (
        select sql_id,count(*) as cn
        from v$active_session_history
        where sample_time > sysdate - 10/24/60
            and session_type <> ‘BACKGROUND‘
            and WAIT_CLASS=‘User I/O‘
        group by sql_id
        order by cn desc
    ) ash, v$sql s
where ash.sql_id=s.sql_id;

--清空缓存，Command window执行：
  Alter system flush shared_pool;

--analyze table 更新统计信息：
  analyze table my_table compute statistics;

--删除数据后，释放数据空间
  alter table my_table enable row movement;
  alter table my_table shrink space cascade;
  alter table my_table disable row movement;

获取指定SQL在内存中的执行计划：
select sql_id,child_number,sql_text from v$sql where sql_text like ‘select count(1) from emp a where a.dept_no =%‘;
select * from table(DBMS_XPLAN.DISPLAY_CURSOR(‘sql_id‘,0)); 

1、PL/SQL Developer 中使用F5
2、explain plan for select count(1) from emp a where a.dept_no=5;
     select * from table(dbms_xplan.display());
3、sqlplus中使用 set autotrace traceonly exp;