ORACLE常用性能监控SQL【一】

目录(?)[+]

系列

ORACLE常用性能监控SQL【一】

ORACLE常用性能监控SQL【二】

Oracle-动态性能视图解读

---

• 系列
• 死锁后的解决办法
  • 生成Kill Session语句
  • 查看导致死锁的 SQL
  • 查看谁锁了谁
• ORA-00054 资源正忙要求指定 NOWAIT
• 查询绑定变量使用的实际值
• 监控事例的等待
• 回滚段的争用情况
• 查看回滚段名称及大小
• 查看控制文件
• 查看日志文件
• 查看前台正在发出的SQL语句
• 数据表占用空间大小情况
• 查看表空间碎片大小
• 查看表空间占用磁盘情况
• 查看表的大小倒序排列
• 查看表空间物理文件的名称及大小
• 查看Oracle 表空间使用率
• 查看Temp 表空间实际使用磁盘大小
• 查看session使用回滚段
• 查看当前临时表空间使用大小与正在占用临时表空间的sql语句
• Temp表空间上进程的查询
• 查看SGA区剩余可用内存
• 监控表空间IO比例
• 监控SGA命中率
• 监控 SGA 中字典缓冲区的命中率
• 监控 SGA 享缓存区的命中率应该小于1
• 监控 SGA 中重做日志缓存区的命中率应该小于1
• 监控内存和硬盘的排序比率最好使它小于 10
• 监控字典缓冲区
• 非系统用户建在SYSTEM表空间中的表
• 性能最差的SQL
• 读磁盘数超100次的sql
• 查找消耗资源比较的sql语句
• 最频繁执行的sql
• 查询使用CPU多的用户session
• 当前每个会话使用的对象数
• 查看数据库库对象
• 查看数据库的版本　
• 查看数据库的创建日期和归档方式
• 检查角色和权限设置
  • 根据用户名进行授权的对象级特权
  • 根据被授权人进行授权的对象级特权
  • 根据用户名进行授予的系统级特权
  • 根据被授权人进行授予的系统级特权
  • 根据用户名授予的角色
  • 根据被授权人授予的角色
  • 用户名及已被授予的相应权限
  • 查询用户名及相应的配置文件默认的表空间和临时表空间
• 等待事件V视图
  • 马上该谁等待查询VSESSION_WAIT VSESSION
  • 马上该谁等待SPECIFIC Waits查询VSESSION_WAIT
  • 谁在等待 - 最后10 个等待数查询VSESSION_WAIT_HISTORY
  • 查找P1 P2 P3代表什么查询 VEVENT_NAME
  • 会话开始后的所有等待数查询 VSESSION_EVENT
  • 类的所有会话等待数查询VSESSION_WAIT_CLASS
  • 系统启动后的所有等待数查询VSYSTEM_EVENT
  • 类的系统等待数查询VSYSTEM_WAIT_CLASS
  • 类的系统等待数查询VACTIVE_SESSION_HISTORY
• 自动工作量仓库AWR 的基本信息
• 获取生成的trace文件

---

死锁后的解决办法

如果死锁不能自动释放，就需要我们手工的 kill session

生成Kill Session语句

1. 查看有无死锁对象，如有 kill session

SELECT 'alter system kill session ''' || sid || ',' || serial# || ''';' "Deadlock"
  FROM v$session
 WHERE sid IN (SELECT sid FROM v$lock WHERE block = 1);

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如果有，会返回类似与如下的信息：

alter system kill session '761,876';
.....

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kill session：
执行 alter system kill session ‘761,876’(sid 为 761);

注意： 应当注意对于 sid 在 100 以下的应当谨慎，可能该进程对应某个application，如对应某个事务,可以 kill

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查看导致死锁的 SQL

SELECT s.sid, q.sql_text
FROM v$sqltext q, v$session s
WHERE q.address = s.sql_address AND s.sid = &sid -- 这个&sid 是第一步查询出来的
ORDER BY piece;

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执行后，输入对应的sid即可查看对应的sql.

---

查看谁锁了谁

SELECT s1.username || '@' || s1.machine || ' ( SID=' || s1.sid ||
       ' ) is blocking ' || s2.username || '@' || s2.machine || ' ( SID=' ||
       s2.sid || ' ) ' AS blocking_status
  FROM v$lock l1, v$session s1, v$lock l2, v$session s2
 WHERE s1.sid = l1.sid
   AND s2.sid = l2.sid
   AND l1.BLOCK = 1
   AND l2.request > 0
   AND l1.id1 = l2.id1
   AND l2.id2 = l2.id2;

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或者

推荐这个，因为使用的是 v$locked_object

SELECT LPAD(' ', DECODE(l.xidusn, 0, 3, 0)) || l.oracle_username User_name,
       o.owner,
       o.object_name,
       o.object_type,
       s.sid,
       s.serial#
  FROM v$locked_object l, dba_objects o, v$session s
 WHERE l.object_id = o.object_id
   AND l.session_id = s.sid
 ORDER BY o.object_id, xidusn DESC;

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V$LOCKED_OBJECT只能报发生等待的表级锁,不能报发生等待的行级锁。

---

ORA-00054 资源正忙，要求指定 NOWAIT

演示：

select * from emp for update ;--通过for update 获取一个排它锁

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SQL>select object_name as 对象名称,s.sid,s.serial#,p.spid as 系统进程号
from v$locked_object l , dba_objects o , v$session s , v$process p
where l.object_id=o.object_id and l.session_id=s.sid and s.paddr=p.addr;

对象名称                                                                         SID    SERIAL# 系统进程号
-------------------------------------------------------------------------------- ---------- ---------- ------------------------
EMP                                                                               1411       8865 32720

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在另外一个会话中执行

ALTER SYSTEM KILL SESSION '1411,8865';

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---

查询绑定变量使用的实际值

1, SQL还在shared pool中，没有被aged out 替换SQL ID 值即可

select sql_id, name, datatype_string, last_captured, value_string
  from v$sql_bind_capture  where sql_id = '7nqt558g5gmyr'  order by LAST_CAPTURED,
       POSITION;

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2.请自行替换sql_id，此时是从awr中查询(sql 被 aged out 出 shared pool)

select instance_number,
         sql_id,
       name,
       datatype_string,
       last_captured,
       value_string
  from dba_hist_sqlbind
 where sql_id = 'fahv8x6ngrb50'
 order by LAST_CAPTURED, POSITION;

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---

监控事例的等待

select event,sum(decode(wait_Time,0,0,1)) "Prev",
sum(decode(wait_Time,0,1,0)) "Curr",count(*) "Tot"
from v$session_Wait
group by event order by 4 ;

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---

回滚段的争用情况

select name, waits, gets, waits / gets "Ratio"
  from v$rollstat a, v$rollname b
 where a.usn = b.usn;

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---

查看回滚段名称及大小

SELECT segment_name,
       tablespace_name,
       r.status,
       (initial_extent / 1024) initialextent,
       (next_extent / 1024) nextextent,
       max_extents,
       v.curext curextent
  FROM dba_rollback_segs r, v$rollstat v
 WHERE r.segment_id = v.usn(+)
 ORDER BY segment_name;

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---

查看控制文件

SELECT NAME FROM v$controlfile; 

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---

查看日志文件

SELECT MEMBER FROM v$logfile;

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---

查看前台正在发出的SQL语句

select user_name,sql_text
　　 from v$open_cursor
　　 where sid in (select sid from (select sid,serial#,username,program
　　 from v$session
　　 where status='ACTIVE'));

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---

数据表占用空间大小情况

select segment_name, tablespace_name, bytes, blocks
  from user_segments
 where segment_type = 'TABLE'
 ORDER BY bytes DESC, blocks DESC;

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---

查看表空间碎片大小

 select tablespace_name,round(sqrt(max(blocks)/sum(blocks))*
           (100/sqrt(sqrt(count(blocks)))),2) FSFI
    from dba_free_space
    group by tablespace_name order by 1;

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---

查看表空间占用磁盘情况

    select
             b.file_id                                 文件ID号,
             b.tablespace_name                         表空间名,
             b.bytes                                 字节数,
             (b.bytes-sum(nvl(a.bytes,0)))                 已使用,
             sum(nvl(a.bytes,0))                         剩余空间,
             sum(nvl(a.bytes,0))/(b.bytes)*100         剩余百分比
             from dba_free_space a,dba_data_files b
             where a.file_id=b.file_id
             group by b.tablespace_name,b.file_id,b.bytes
             order by b.file_id;

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---

查看表的大小，倒序排列

每张表都是作为“段”来存储的，可以通过user_segments视图查看其相应信息。
段（segments）的定义：如果创建一个堆组织表，则该表就是一个段

SELECT SEGMENT_NAME, SUM(BYTES) / 1024 / 1024 MBYTESE
  FROM USER_SEGMENTS
 WHERE SEGMENT_TYPE = 'TABLE'
 GROUP BY SEGMENT_NAME
 order by MBYTESE desc;

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---

查看表空间物理文件的名称及大小

SELECT tablespace_name,
       file_id,
       file_name,
       round(bytes / (1024 * 1024), 0) total_space
  FROM dba_data_files
 ORDER BY tablespace_name;

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---

查看Oracle 表空间使用率

SELECT D.TABLESPACE_NAME,
       SPACE || 'M' "SUM_SPACE(M)",
       SPACE - NVL (FREE_SPACE, 0) || 'M' "USED_SPACE(M)",
       ROUND ( (1 - NVL (FREE_SPACE, 0) / SPACE) * 100, 2) || '%'
          "USED_RATE(%)",
       FREE_SPACE || 'M' "FREE_SPACE(M)"
  FROM (  SELECT TABLESPACE_NAME,
                 ROUND (SUM (BYTES) / (1024 * 1024), 2) SPACE,
                 SUM (BLOCKS) BLOCKS
            FROM DBA_DATA_FILES
        GROUP BY TABLESPACE_NAME) D,
       (  SELECT TABLESPACE_NAME,
                 ROUND (SUM (BYTES) / (1024 * 1024), 2) FREE_SPACE
            FROM DBA_FREE_SPACE
        GROUP BY TABLESPACE_NAME) F
 WHERE D.TABLESPACE_NAME = F.TABLESPACE_NAME(+)
UNION ALL                                                           --如果有临时表空间
SELECT D.TABLESPACE_NAME,
       SPACE || 'M' "SUM_SPACE(M)",
       USED_SPACE || 'M' "USED_SPACE(M)",
       ROUND (NVL (USED_SPACE, 0) / SPACE * 100, 2) || '%' "USED_RATE(%)",
       NVL (FREE_SPACE, 0) || 'M' "FREE_SPACE(M)"
  FROM (  SELECT TABLESPACE_NAME,
                 ROUND (SUM (BYTES) / (1024 * 1024), 2) SPACE,
                 SUM (BLOCKS) BLOCKS
            FROM DBA_TEMP_FILES
        GROUP BY TABLESPACE_NAME) D,
       (  SELECT TABLESPACE_NAME,
                 ROUND (SUM (BYTES_USED) / (1024 * 1024), 2) USED_SPACE,
                 ROUND (SUM (BYTES_FREE) / (1024 * 1024), 2) FREE_SPACE
            FROM V$TEMP_SPACE_HEADER
        GROUP BY TABLESPACE_NAME) F
 WHERE D.TABLESPACE_NAME = F.TABLESPACE_NAME(+)
ORDER BY 1;

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SELECT a.tablespace_name "表空间名",
       total "表空间大小",
       free "表空间剩余大小",
       (total - free) "表空间使用大小",
       total / (1024 * 1024 * 1024) "表空间大小(G)",
       free / (1024 * 1024 * 1024) "表空间剩余大小(G)",
       (total - free) / (1024 * 1024 * 1024) "表空间使用大小(G)",
       round((total - free) / total, 4) * 100 "使用率 %"
  FROM (SELECT tablespace_name, SUM(bytes) free
          FROM dba_free_space
         GROUP BY tablespace_name) a,
       (SELECT tablespace_name, SUM(bytes) total
          FROM dba_data_files
         GROUP BY tablespace_name) b
 WHERE a.tablespace_name = b.tablespace_name

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---

查看Temp 表空间实际使用磁盘大小

Select f.tablespace_name,
       d.file_name "Tempfile name",
       round((f.bytes_free + f.bytes_used) / 1024 / 1024, 2) "total MB",
       round(((f.bytes_free + f.bytes_used) - nvl(p.bytes_used, 0)) / 1024 / 1024,
             2) "Free MB",
       round(nvl(p.bytes_used, 0) / 1024 / 1024, 2) "Used MB",
       round((round(nvl(p.bytes_used, 0) / 1024 / 1024, 2) /
             round((f.bytes_free + f.bytes_used) / 1024 / 1024, 2)) * 100,
             2) as "Used_Rate(%)"
  from SYS.V_$TEMP_SPACE_HEADER f,
       DBA_TEMP_FILES           d,
       SYS.V_$TEMP_EXTENT_POOL  p
 where f.tablespace_name(+) = d.tablespace_name
   and f.file_id(+) = d.file_id
   and p.file_id(+) = d.file_id;

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---

查看session使用回滚段

SELECT  r.name 回滚段名,
        s.sid,
        s.serial#,
        s.username 用户名,
        t.status,
        t.cr_get,
        t.phy_io,
        t.used_ublk,
        t.noundo,
        substr(s.program, 1, 78) 操作程序
FROM   sys.v_$session s,sys.v_$transaction t,sys.v_$rollname r
WHERE  t.addr = s.taddr and t.xidusn = r.usn
ORDER  BY t.cr_get,t.phy_io;

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---

查看当前临时表空间使用大小与正在占用临时表空间的sql语句

   select sess.SID, segtype, blocks * 8 / 1000 "MB", sql_text
     from v$sort_usage sort, v$session sess, v$sql sql
    where sort.SESSION_ADDR = sess.SADDR
      and sql.ADDRESS = sess.SQL_ADDRESS
    order by blocks desc;

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---

Temp表空间上进程的查询

select a.tablespace, b.sid, b.serial#, a.blocks,c.sql_text
  from v$sort_usage a,v$session b,v$sqltext c
 where a.session_addr = b.saddr
   and b.sql_address = c.address
 order by a.tablespace,b.sid,b.serial#,c.address, c.piece;

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---

查看SGA区剩余可用内存

select name,
　　　　　　sgasize/1024/1024　　　　　　　　"Allocated(M)",
　　　　　　bytes/1024　　　　　　　　　　　 "**空间(K)",
　　　　　　round(bytes/sgasize*100, 2)　　　"**空间百分比(%)"
　　 from   (select sum(bytes) sgasize from sys.v_$sgastat) s, sys.v_$sgastat f
　　 where  f.name = 'free memory';

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---

监控表空间I/O比例

select df.tablespace_name name,df.file_name "file",f.phyrds pyr,
       f.phyblkrd pbr,f.phywrts pyw, f.phyblkwrt pbw
from v$filestat f, dba_data_files df
where f.file# = df.file_id
order by df.tablespace_name;

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---

监控SGA命中率

select a.value + b.value "logical_reads",
       c.value "phys_reads",
       round(100 * ((a.value+b.value)-c.value) / (a.value+b.value)) "BUFFER HIT RATIO"
from v$sysstat a, v$sysstat b, v$sysstat c
where a.statistic# = 38 and
      b.statistic# = 39 and
      c.statistic# = 40 ;

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---

监控 SGA 中字典缓冲区的命中率

select parameter, gets,Getmisses , getmisses/(gets+getmisses)*100 "miss ratio",
(1-(sum(getmisses)/ (sum(gets)+sum(getmisses))))*100 "Hit ratio"
from v$rowcache
where gets+getmisses <>0
group by parameter, gets, getmisses ;

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---

监控 SGA **享缓存区的命中率，应该小于1%

select sum(pins) "Total Pins", sum(reloads) "Total Reloads",
sum(reloads)/sum(pins) *100 libcache
from v$librarycache;

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---

监控 SGA 中重做日志缓存区的命中率，应该小于1%

SELECT name, gets, misses, immediate_gets, immediate_misses,
Decode(gets,0,0,misses/gets*100) ratio1,
Decode(immediate_gets+immediate_misses,0,0,
immediate_misses/(immediate_gets+immediate_misses)*100) ratio2
FROM v$latch WHERE name IN ('redo allocation', 'redo copy');

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---

监控内存和硬盘的排序比率，最好使它小于 .10

SELECT name, value
FROM v$sysstat
WHERE name IN ('sorts (memory)', 'sorts (disk)') ;

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---

监控字典缓冲区

SELECT SUM(GETS) "DICTIONARY GETS",SUM(GETMISSES) "DICTIONARY CACHE GET MISSES"
FROM V$ROWCACHE ;

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---

非系统用户建在SYSTEM表空间中的表

SELECT owner,table_name
FROM DBA_TABLES
WHERE tablespace_name in('SYSTEM','USER_DATA') AND
      owner NOT IN('SYSTEM','SYS','OUTLN', 'ORDSYS','MDSYS','SCOTT', 'HOSTEAC');

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---

性能最差的SQL

SELECT * FROM ( SELECT PARSING_USER_ID EXECUTIONS,SORTS,COMMAND_TYPE,DISK_READS,sql_text
                FROM v$sqlarea
                ORDER BY disk_reads DESC)
WHERE ROWNUM<100;

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---

读磁盘数超100次的sql

select * from sys.v_$sqlarea where disk_reads>100;

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---

查找消耗资源比较的sql语句

  Select se.username,
          se.sid,
          su.extents,
          su.blocks * to_number(rtrim(p.value)) as Space,
          tablespace,
          segtype,
          sql_text
     from v$sort_usage su, v$parameter p, v$session se, v$sql s
    where p.name = 'db_block_size'
      and su.session_addr = se.saddr
      and s.hash_value = su.sqlhash
      and s.address = su.sqladdr
    order by se.username, se.sid;

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---

最频繁执行的sql

select * from sys.v_$sqlarea where executions>100;

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---

查询使用CPU多的用户session

select a.sid,spid,status,substr(a.program,1,40) prog,a.terminal,osuser,value/60/100 value
from v$session a,v$process b,v$sesstat c
where c.statistic#=12 and
      c.sid=a.sid and
      a.paddr=b.addr
order by value desc;

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---

当前每个会话使用的对象数

SELECT a.sid,s.terminal,s.program,count(a.sid)
FROM V$ACCESS a,V$SESSION s
WHERE a.owner <> 'SYS'AND s.sid = a.sid
GROUP BY a.sid,s.terminal,s.program
ORDER BY count(a.sid) ;

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---

查看数据库库对象

SELECT owner, object_type, status, COUNT(*) count#
  FROM all_objects
 GROUP BY owner, object_type, status;

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---

查看数据库的版本　

SELECT version
FROM product_component_version
WHERE substr(product, 1, 6) = 'Oracle'; 

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---

查看数据库的创建日期和归档方式

SELECT created, log_mode, log_mode FROM v$database; 

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---

检查角色和权限设置

根据用户名进行授权的对象级特权

select b.owner || '.' || b.table_name obj,
       b.privilege what_granted,
       b.grantable,
       a.username
  from sys.dba_users a, sys.dba_tab_privs b
 where a.username = b.grantee
 order by 1, 2, 3;

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根据被授权人进行授权的对象级特权

Select owner || '.' || table_name obj,
       privilege what_granted,
       grantable,
       grantee
  from sys.dba_tab_privs
 where not exists (select 'x' from sys.dba_users where username = grantee)
 order by 1, 2, 3;

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根据用户名进行授予的系统级特权

select b.privilege what_granted, b.admin_option, a.username
  from sys.dba_users a, sys.dba_sys_privs b
 where a.username = b.grantee
 order by 1, 2;

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根据被授权人进行授予的系统级特权

select privilege what_granted, admin_option, grantee
  from sys.dba_sys_privs
 where not exists (select 'x' from sys.dba_users where username = grantee)
 order by 1, 2;

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根据用户名授予的角色

select b.granted_role ||
       decode(admin_option, 'YES', ' (With Admin Option)', null) what_granted,
       a.username
  from sys.dba_users a, sys.dba_role_privs b
 where a.username = b.grantee
 order by 1;

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根据被授权人授予的角色

select granted_role ||
       decode(admin_option, 'YES', ' (With Admin Option)', null) what_granted,
       grantee
  from sys.dba_role_privs
 where not exists (select 'x' from sys.dba_users where username = grantee)
 order by 1;

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用户名及已被授予的相应权限

select a.username,
       b.granted_role ||
       decode(admin_option, 'YES', ' (With Admin Option)', null) what_granted
  from sys.dba_users a, sys.dba_role_privs b
 where a.username = b.grantee
UNION
select a.username,
       b.privilege ||
       decode(admin_option, 'YES', ' (With Admin Option)', null) what_granted
  from sys.dba_users a, sys.dba_sys_privs b
 where a.username = b.grantee
UNION
select a.username,
       b.table_name || '-' || b.privilege ||
       decode(grantable, 'YES', ' (With Grant Option)', null) what_granted
  from sys.dba_users a, sys.dba_tab_privs b
 where a.username = b.grantee
 order by 1;

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查询用户名及相应的配置文件、默认的表空间和临时表空间

Select username, profile, default_tablespace, temporary_tablespace, created
  from sys.dba_users
 order by username;

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---

等待事件V$视图

在Oracle 10g中V$SESSION_WAIT中的所有等待事件列现在都在V$SESSION中。因此，确保查询等待信息的 V$SESSION，因为它是一个更快的视图。V$ACTIVE_SESSION_HISTORY (ASH)将许多重要统计数据合并为一个视图或一个报表(ASH报表)。

马上该谁等待–查询V$SESSION_WAIT / V$SESSION

select event,
       sum(decode(wait_time, 0, 1, 0)) "Waiting Now",
       sum(decode(wait_time, 0, 0, 1)) "Previous Waits",
       count(*) "Total"
  from v$session_wait
 group by event
 order by count(*);

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马上该谁等待；SPECIFIC Waits–查询V$SESSION_WAIT

SELECT /*+ ordered */
 sid, event, owner, segment_name, segment_type, p1, p2, p3
  FROM v$session_wait sw, dba_extents de
 WHERE de.file_id = sw.p1
   AND sw.p2 between de.block_id and de.block_id + de.blocks - 1
   AND (event = 'buffer busy waits' OR event = 'write complete waits')
   AND p1 IS NOT null
 ORDER BY event, sid;

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谁在等待 - 最后10 个等待数–查询V$SESSION_WAIT_HISTORY

SELECT /*+ ordered */
 sid, event, owner, segment_name, segment_type, p1, p2, p3
  FROM v$session_wait sw, dba_extents de
 WHERE de.file_id = sw.p1
   AND sw.p2 between de.block_id and de.block_id + de.blocks - 1
   AND (event = 'buffer busy waits' OR event = 'write complete waits')
   AND p1 IS NOT null
 ORDER BY event, sid;

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查找P1, P2, P3代表什么–查询 V$EVENT_NAME

select event#, name, parameter1 p1, parameter2 p2, parameter3 p3
  from v$event_name
 where name in ('buffer busy waits', 'write complete waits');

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会话开始后的所有等待数–查询 V$SESSION_EVENT

select sid, event, total_waits, time_waited, event_id
  from v$session_event
 where time_waited > 0
 order by time_waited;

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类的所有会话等待数–查询V$SESSION_WAIT_CLASS

select sid, wait_class, total_waits from  v$session_wait_class;

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系统启动后的所有等待数–查询V$SYSTEM_EVENT

select event, total_waits, time_waited, event_id
  from v$system_event
 where time_waited > 0
 order by time_waited;

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类的系统等待数–查询V$SYSTEM_WAIT_CLASS

select wait_class, total_waits
  from v$system_wait_class
 order by total_waits desc;

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类的系统等待数–查询V$ACTIVE_SESSION_HISTORY

–In the query below, the highest count session is leader in non-idle wait events.

select session_id, count(1)
  from v$active_session_history
 group by session_id
 order by 2;

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–In the query below, find the SQL for the leader in non-idle wait events.

select c.sql_id, a.sql_text
  from v$sql a,
       (select sql_id, count(1)
          from v$active_session_history b
         where sql_id is not null
         group by sql_id order by 2 desc) c
 where rownum <= 5
 order by rownum;

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自动工作量仓库(AWR) 的基本信息

自动工作量仓库(AWR)在默认情况下，仓库用小时填充，保留期是7天。
AWR使用多少空间

SQL> Select occupant_name,occupant_desc,space_usage_kbytes from v$sysaux_occupants where occupant_name like '%AWR%';

OCCUPANT_NAME       OCCUPANT_DESC            SPACE_USAGE_KBYTES
----------------- ---------------------------------- ------------------
SM/AWR        Server Manageability - Automatic Workload Repository             215616

SQL> 

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系统上最原始的AWR信息是什么？

SQL> select dbms_stats.get_stats_history_availability from dual;

GET_STATS_HISTORY_AVAILABILITY
-------------------------------------------------------------
20-OCT-16 12.04.49.088829000 AM -04:00

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什么是AWR信息的保留期？

SQL>  select dbms_stats.get_stats_history_retention from dual;

GET_STATS_HISTORY_RETENTION
---------------------------
                         31

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将AWR信息的保留期更改为15天？

SQL> EXEC dbms_stats.alter_stats_history_retention(15);
PL/SQL 过程已成功完成。

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---

获取生成的trace文件

开启SQL跟踪后，会生成一个trace文件，通过初始化参数user_dump_dest配置其所在目录，该参数的值可以通过下面方法获取到：

select name, value from v$parameter where name = 'user_dump_dest'

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trace文件的名字是独立于版本和平台的，在大部分常见的平台下，命名结构如下：

{instance name}_{process name}_{process id}.trc

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1）instance name
初始化参数instance_name的小写值。通过v$instance视图的instance_name列可以得到这个值。
2）process name
产生跟踪文件进程的名字的小写值。对于专有服务器进程，使用ora，对于共享服务器进程，可以通过v$diapatcher或v$shared_server视图的name列获得。对于并行从属进程，可以通过v$px_process视图server_name列获得，对于其他多数后台进程来说，可以通过v$bgprocess视图的name列获得。
3）process id
操作系统层面的进程标记。这个值可以通过v$process视图的spid列获取。

根据这些信息，可以通过下面的方式获取trace文件名：

select s.SID,
       s.SERVER,
       lower(case
               when s.SERVER in ('DEDICATED', 'SHARED') then
                i.INSTANCE_NAME || '_' || nvl(pp.SERVER_NAME, nvl(ss.NAME, 'ora')) || '_' ||
                p.SPID || '.trc'
               else
                null
             end) as trace_file_name
  from v$instance      i,
       v$session       s,
       v$process       p,
       v$px_process    pp,
       v$shared_server ss
 where s.PADDR = p.ADDR
   and s.SID = pp.SID(+)
   and s.PADDR = ss.PADDR(+)
   and s.TYPE = 'USER'
   and s.SID = 'your sid'
 order by s.SID

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将上面的’your sid’替换为你的session的sid就可以查出指定session生成的trace文件的名字，session的sid在v$session视图中得到，或者直接查询当前session的sid：

select userenv('sid') from dual
或者
select  sid  from v$mystat a where rownum=1 ;               

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将路径（user_dump_dest）和文件名结合在一起，我们就得到了trace文件的完整路径。

而在Oracel 11g中，查询当前会话生成的trace文件则非常简单：

select value from v$diag_info where name = 'Default Trace File'