--查詢最慢的sql
select * from (
select parsing_user_id,executions,sorts
command_type,disk_reads,sql_text from v$sqlarea order by disk_reads desc
)where rownum<10
--查詢對應session
select SE.SID,SE.SERIAL#,PR.SPID,
SE.USERNAME,SE.STATUS,SE.TERMINAL,
SE.PROGRAM,SE.MODULE,
SE.SQL_ADDRESS,ST.EVENT,
ST.P1TEXT,SI.PHYSICAL_READS,SI.BLOCK_CHANGES from v$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：存儲的是完整的SQL,SQL被分割
v$sqlarea：存儲的SQL 和一些相關的信息，比如累計的執行次數，邏輯讀，物理讀等統計信息（統計）
v$sql：內存共享SQL區域中已經解析的SQL語句。（即時）
根據sid查找完整sql語句：
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時間 百萬分之一（微秒）
a.OPTIMIZER_MODE,--優化方式
a.EXECUTIONS,--執行次數
a.DISK_READS,--讀盤次數
a.SHARABLE_MEM,--占用shared pool的內存多少
a.BUFFER_GETS,--讀取緩沖區的次數
a.COMMAND_TYPE,--命令類型(3:select,2:insert;6:update;7delete;47:pl/sql程序單元)
a.SQL_TEXT,--Sql語句
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_$SQLAREA a
WHERE PARSING_SCHEMA_NAME = 'CHEA_FILL'--表空間
order by a.CPU_TIME desc
引用：http://jenniferok.iteye.com/blog/700985
a.executions exec,a.disk_reads/decode(a.executions,0,1,a.executions) rds_exec_ratio,
a.sql_text Statement
from v$sqlarea a,dba_users b
where a.parsing_user_id=b.user_id
and a.disk_reads > 100000
order by a.disk_reads desc;
列出使用頻率最高的5個查詢：
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;
找出需要大量緩沖讀取（邏輯讀）操作的查詢：
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個字符 |
SQL_ID |
VARCHAR2(13) |
SQL identifier of the parent cursor in the library cache |
SHARABLE_MEM |
NUMBER |
占用的共享內存大小 (單位： byte) |
PERSISTENT_MEM |
NUMBER |
生命期內的固定內存大小 (單位： byte) |
RUNTIME_MEM |
NUMBER |
執行期內的固定內存大小 |
SORTS |
NUMBER |
完成的排序數 |
VERSION_COUNT |
NUMBER |
Number of child cursors that are present in the cache under this parent |
LOADED_VERSIONS |
NUMBER |
顯示上下文堆是否載入， 1是 0否 |
OPEN_VERSIONS |
NUMBER |
顯示子游標是否被鎖， 1是 0否 |
USERS_OPENING |
NUMBER |
執行語句的用戶數 |
FETCHES |
NUMBER |
SQL語句的 fetch數。 |
EXECUTIONS |
NUMBER |
自它被載入緩存庫后的執行次數 |
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 |
執行語句的用戶數 |
LOADS |
NUMBER |
對象被載入過的次數 |
FIRST_LOAD_TIME |
VARCHAR2(19) |
初次載入時間 |
INVALIDATIONS |
NUMBER |
無效的次數 |
PARSE_CALLS |
NUMBER |
解析調用次數 |
DISK_READS |
NUMBER |
讀磁盤次數 |
DIRECT_WRITES |
NUMBER |
Sum of the number of direct writes over all child cursors |
BUFFER_GETS |
NUMBER |
讀緩存區次數 |
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語句返回的總列數 |
COMMAND_TYPE |
NUMBER |
命令類型代號 |
OPTIMIZER_MODE |
VARCHAR2(25) |
QL語句的優化器模型 |
PARSING_USER_ID |
NUMBER |
第一個解析的用戶 ID |
PARSING_SCHEMA_ID |
NUMBER |
第一個解析的計划 ID |
KEPT_VERSIONS |
NUMBER |
指出是否當前子游標被使用 DBMS_SHARED_POOL包標記為常駐內存 |
ADDRESS |
RAW(4 | 8) |
當前游標父句柄地址 |
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 |
來源：http://blog.csdn.net/sxhong/article/details/18262663
有很多種方法可以用來找出哪些SQL語句需要優化，但是很久以來，最簡單的方法都是分析保存在V$SQL視圖中的緩存的SQL信息。通過V$SQL視圖，可以確定具有高消耗時間、CUP和IO讀取的SQL語句。
1.查看總消耗時間最多的前10條SQL語句
select *
from (select v.sql_id,
v.child_number,
v.sql_text,
v.elapsed_time,
v.cpu_time,
v.disk_reads,
rank() over(order by v.elapsed_time desc) elapsed_rank
from v$sql v) a
where elapsed_rank <= 10;
2.查看CPU消耗時間最多的前10條SQL語句
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$sql v) a
where elapsed_rank <= 10;
3.查看消耗磁盤讀取最多的前10條SQL語句
select *
from (select v.sql_id,
v.child_number,
v.sql_text,
v.elapsed_time,
v.cpu_time,
v.disk_reads,
rank() over(order by v.disk_reads desc) elapsed_rank
from v$sql v) a
where elapsed_rank <= 10;
查詢執行最慢的sql
select *
from (select sa.SQL_TEXT,
sa.SQL_FULLTEXT,
sa.EXECUTIONS "執行次數",
round(sa.ELAPSED_TIME / 1000000, 2) "總執行時間",
round(sa.ELAPSED_TIME / 1000000 / sa.EXECUTIONS, 2) "平均執行時間",
sa.COMMAND_TYPE,
sa.PARSING_USER_ID "用戶ID",
u.username "用戶名",
sa.HASH_VALUE
from v$sqlarea sa
left join all_users u
on sa.PARSING_USER_ID = u.user_id
where sa.EXECUTIONS > 0
order by (sa.ELAPSED_TIME / sa.EXECUTIONS) desc)
where rownum <= 50;
查詢次數最多的 sql
select *
from (select s.SQL_TEXT,
s.EXECUTIONS "執行次數",
s.PARSING_USER_ID "用戶名",
rank() over(order by EXECUTIONS desc) EXEC_RANK
from v$sql s
left join all_users u
on u.USER_ID = s.PARSING_USER_ID) t
where exec_rank <= 100;