--查询最慢的sql
select * from (
select parsing_user_id,executions,sorts
command_type,disk_reads,sql_text from v$sqlarea order by disk_reads desc
)where rownum<10
--查询对应session
select SE.SID,SE.SERIAL#,PR.SPID,
SE.USERNAME,SE.STATUS,SE.TERMINAL,
SE.PROGRAM,SE.MODULE,
SE.SQL_ADDRESS,ST.EVENT,
ST.P1TEXT,SI.PHYSICAL_READS,SI.BLOCK_CHANGES from v$session se,v$session_wait st,
v$sess_io si,v$process pr
where st.SID=se.SID and st.SID=si.SID
AND SE.PADDR=PR.ADDR
AND SE.SID>6
AND ST.WAIT_TIME=0
AND ST.EVENT NOT LIKE '%SQL%'
ORDER BY PHYSICAL_READS DESC;
SELECT sql_address FROM V$SESSION SS,V$SQLTEXT TT
WHERE SS.SQL_HASH_VALUE=TT.HASH_VALUE AND SID=439;
v$sqltext：存储的是完整的SQL,SQL被分割
v$sqlarea：存储的SQL 和一些相关的信息，比如累计的执行次数，逻辑读，物理读等统计信息（统计）
v$sql：内存共享SQL区域中已经解析的SQL语句。（即时）
根据sid查找完整sql语句：
select sql_text from v$sqltext a where a.hash_value = (select sql_hash_value from v$session b where b.sid = '&sid' )
order by piece asc
select a.CPU_TIME,--CPU时间 百万分之一（微秒）
a.OPTIMIZER_MODE,--优化方式
a.EXECUTIONS,--执行次数
a.DISK_READS,--读盘次数
a.SHARABLE_MEM,--占用shared pool的内存多少
a.BUFFER_GETS,--读取缓冲区的次数
a.COMMAND_TYPE,--命令类型(3:select,2:insert;6:update;7delete;47:pl/sql程序单元)
a.SQL_TEXT,--Sql语句
a.SHARABLE_MEM,
a.PERSISTENT_MEM,
a.RUNTIME_MEM,
a.PARSE_CALLS,
a.DISK_READS,
a.DIRECT_WRITES,
a.CONCURRENCY_WAIT_TIME,
a.USER_IO_WAIT_TIME
from SYS.V_$SQLAREA a
WHERE PARSING_SCHEMA_NAME = 'CHEA_FILL'--表空间
order by a.CPU_TIME desc
引用：http://jenniferok.iteye.com/blog/700985
a.executions exec,a.disk_reads/decode(a.executions,0,1,a.executions) rds_exec_ratio,
a.sql_text Statement
from v$sqlarea a,dba_users b
where a.parsing_user_id=b.user_id
and a.disk_reads > 100000
order by a.disk_reads desc;
列出使用频率最高的5个查询：
from (select sql_text,executions,
rank() over
(order by executions desc) exec_rank
from v$sql)
where exec_rank <=5;
select disk_reads,sql_text
from (select sql_text,disk_reads,
dense_rank() over
(order by disk_reads desc) disk_reads_rank
from v$sql)
where disk_reads_rank <=5;
找出需要大量缓冲读取（逻辑读）操作的查询：
from (select sql_text,buffer_gets,
dense_rank() over
(order by buffer_gets desc) buffer_gets_rank
from v$sql)
where buffer_gets_rank<=5;
SQL_TEXT |
VARCHAR2(1000) |
SQL文本的前 1000个字符 |
SQL_ID |
VARCHAR2(13) |
SQL identifier of the parent cursor in the library cache |
SHARABLE_MEM |
NUMBER |
占用的共享内存大小 (单位： byte) |
PERSISTENT_MEM |
NUMBER |
生命期内的固定内存大小 (单位： byte) |
RUNTIME_MEM |
NUMBER |
执行期内的固定内存大小 |
SORTS |
NUMBER |
完成的排序数 |
VERSION_COUNT |
NUMBER |
Number of child cursors that are present in the cache under this parent |
LOADED_VERSIONS |
NUMBER |
显示上下文堆是否载入， 1是 0否 |
OPEN_VERSIONS |
NUMBER |
显示子游标是否被锁， 1是 0否 |
USERS_OPENING |
NUMBER |
执行语句的用户数 |
FETCHES |
NUMBER |
SQL语句的 fetch数。 |
EXECUTIONS |
NUMBER |
自它被载入缓存库后的执行次数 |
END_OF_FETCH_COUNT |
NUMBER |
Number of times this cursor was fully executed since the cursor was brought into the library cache. The value of this statistic is not incremented when the cursor is partially executed, either because it failed during the execution or because only the first few rows produced by this cursor are fetched before the cursor is closed or re-executed. By definition, the value of theEND_OF_FETCH_COUNT column should be less or equal to the value of the EXECUTIONS column. |
USERS_EXECUTING |
NUMBER |
执行语句的用户数 |
LOADS |
NUMBER |
对象被载入过的次数 |
FIRST_LOAD_TIME |
VARCHAR2(19) |
初次载入时间 |
INVALIDATIONS |
NUMBER |
无效的次数 |
PARSE_CALLS |
NUMBER |
解析调用次数 |
DISK_READS |
NUMBER |
读磁盘次数 |
DIRECT_WRITES |
NUMBER |
Sum of the number of direct writes over all child cursors |
BUFFER_GETS |
NUMBER |
读缓存区次数 |
APPLICATION_WAIT_TIME |
NUMBER |
Application wait time |
CONCURRENCY_WAIT_TIME |
NUMBER |
Concurrency wait time |
CLUSTER_WAIT_TIME |
NUMBER |
Cluster wait time |
USER_IO_WAIT_TIME |
NUMBER |
User I/O Wait Time |
PLSQL_EXEC_TIME |
NUMBER |
PL/SQL execution time |
JAVA_EXEC_TIME |
NUMBER |
Java execution time |
ROWS_PROCESSED |
NUMBER |
解析 SQL语句返回的总列数 |
COMMAND_TYPE |
NUMBER |
命令类型代号 |
OPTIMIZER_MODE |
VARCHAR2(25) |
QL语句的优化器模型 |
PARSING_USER_ID |
NUMBER |
第一个解析的用户 ID |
PARSING_SCHEMA_ID |
NUMBER |
第一个解析的计划 ID |
KEPT_VERSIONS |
NUMBER |
指出是否当前子游标被使用 DBMS_SHARED_POOL包标记为常驻内存 |
ADDRESS |
RAW(4 | 8) |
当前游标父句柄地址 |
HASH_VALUE |
NUMBER |
Hash value of the parent statement in the library cache |
OLD_HASH_VALUE |
NUMBER |
Old SQL hash value |
MODULE |
VARCHAR2(64) |
Contains the name of the module that was executing at the time that the SQL statement was first parsed as set by calling DBMS_APPLICATION_INFO .SET_MODULE |
MODULE_HASH |
NUMBER |
Hash value of the module that is named in the MODULEcolumn |
ACTION |
VARCHAR2(64) |
Contains the name of the action that was executing at the time that the SQL statement was first parsed as set by calling DBMS_APPLICATION_INFO .SET_ACTION |
ACTION_HASH |
NUMBER |
Hash value of the action that is named in the ACTIONcolumn |
SERIALIZABLE_ABORTS |
NUMBER |
Number of times the transaction fails to serialize, producing ORA-08177 errors, totalled over all the child cursors |
CPU_TIME |
NUMBER |
CPU time (in microseconds) used by this cursor for parsing/executing/fetching |
ELAPSED_TIME |
NUMBER |
Elapsed time (in microseconds) used by this cursor for parsing/executing/fetching |
IS_OBSOLETE |
VARCHAR2(1) |
Indicates whether the cursor has become obsolete (Y ) or not (N ). This can happen if the number of child cursors is too large. |
CHILD_LATCH |
NUMBER |
Child latch number that is protecting the cursor |
PROGRAM_ID |
NUMBER |
Program identifie |
来源：http://blog.csdn.net/sxhong/article/details/18262663
有很多种方法可以用来找出哪些SQL语句需要优化，但是很久以来，最简单的方法都是分析保存在V$SQL视图中的缓存的SQL信息。通过V$SQL视图，可以确定具有高消耗时间、CUP和IO读取的SQL语句。
1.查看总消耗时间最多的前10条SQL语句
select *
from (select v.sql_id,
v.child_number,
v.sql_text,
v.elapsed_time,
v.cpu_time,
v.disk_reads,
rank() over(order by v.elapsed_time desc) elapsed_rank
from v$sql v) a
where elapsed_rank <= 10;
2.查看CPU消耗时间最多的前10条SQL语句
select *
from (select v.sql_id,
v.child_number,
v.sql_text,
v.elapsed_time,
v.cpu_time,
v.disk_reads,
rank() over(order by v.cpu_time desc) elapsed_rank
from v$sql v) a
where elapsed_rank <= 10;
3.查看消耗磁盘读取最多的前10条SQL语句
select *
from (select v.sql_id,
v.child_number,
v.sql_text,
v.elapsed_time,
v.cpu_time,
v.disk_reads,
rank() over(order by v.disk_reads desc) elapsed_rank
from v$sql v) a
where elapsed_rank <= 10;
查询执行最慢的sql
select *
from (select sa.SQL_TEXT,
sa.SQL_FULLTEXT,
sa.EXECUTIONS "执行次数",
round(sa.ELAPSED_TIME / 1000000, 2) "总执行时间",
round(sa.ELAPSED_TIME / 1000000 / sa.EXECUTIONS, 2) "平均执行时间",
sa.COMMAND_TYPE,
sa.PARSING_USER_ID "用户ID",
u.username "用户名",
sa.HASH_VALUE
from v$sqlarea sa
left join all_users u
on sa.PARSING_USER_ID = u.user_id
where sa.EXECUTIONS > 0
order by (sa.ELAPSED_TIME / sa.EXECUTIONS) desc)
where rownum <= 50;
查询次数最多的 sql
select *
from (select s.SQL_TEXT,
s.EXECUTIONS "执行次数",
s.PARSING_USER_ID "用户名",
rank() over(order by EXECUTIONS desc) EXEC_RANK
from v$sql s
left join all_users u
on u.USER_ID = s.PARSING_USER_ID) t
where exec_rank <= 100;