转载自:http://www.cnblogs.com/liuweihua/archive/2012/05/05/2484446.html
--top 10 sql
SELECT *
FROM (SELECT b.username username,
a.disk_reads
/ DECODE (a.executions, 0, 1, a.executions) rds_exec_ratio,
a.sql_text STATEMENT
FROM v$sqlarea a, dba_users b
WHERE a.parsing_user_id = b.user_id AND b.username = 'ZYK'
ORDER BY rds_exec_ratio DESC)
WHERE ROWNUM
1. 识别’低效执行’的SQL语句 用下列SQL工具找出低效SQL:
SELECT EXECUTIONS , DISK_READS, BUFFER_GETS,
ROUND((BUFFER_GETS-DISK_READS)/BUFFER_GETS,2) Hit_radio,
ROUND(DISK_READS/EXECUTIONS,2) Reads_per_run,
SQL_TEXT
FROM V$SQLAREA
WHERE EXECUTIONS>0 AND BUFFER_GETS > 0 AND (BUFFER_GETS-DISK_READS)/BUFFER_GETS
2.查找单条语句的内存占用率
alter system set pga_aggregate_target=10m
alter system set workarea_size_policy=auto;
select distinct * from a where rownum<500000;
select sql_text,operation_type,policy,(last_memory_used/1024/1024),
last_execution,last_tempseg_size
from v$sql i,v$sql_workarea a
where i.hash_value=a.hash_value
and sql_text=&#39;select distinct * from a where rownum<500000&#39;;
Top 10 by Buffer Gets:
set linesize 100 set pagesize 100 SELECT * FROM (SELECT substr(sql_text,1,40) sql,
buffer_gets, executions, buffer_gets/executions "Gets/Exec",
hash_value,address
FROM V$SQLAREA
WHERE buffer_gets > 10000 ORDER BY buffer_gets DESC)
WHERE rownum <= 10 ;
Top 10 by Physical Reads:
set linesize 100 set pagesize 100 SELECT * FROM (SELECT substr(sql_text,1,40) sql,
disk_reads, executions, disk_reads/executions "Reads/Exec",
hash_value,address
FROM V$SQLAREA
WHERE disk_reads > 1000 ORDER BY disk_reads DESC)
WHERE rownum <= 10 ;
Top 10 by Executions:
set linesize 100 set pagesize 100 SELECT * FROM (SELECT substr(sql_text,1,40) sql,
executions, rows_processed, rows_processed/executions "Rows/Exec",
hash_value,address
FROM V$SQLAREA
WHERE executions > 100 ORDER BY executions DESC)
WHERE rownum <= 10 ;
Top 10 by Parse Calls:
set linesize 100 set pagesize 100 SELECT * FROM (SELECT substr(sql_text,1,40) sql,
parse_calls, executions, hash_value,address
FROM V$SQLAREA
WHERE parse_calls > 1000 ORDER BY parse_calls DESC)
WHERE rownum <= 10 ;
Top 10 by Sharable Memory:
set linesize 100 set pagesize 100 SELECT * FROM (SELECT substr(sql_text,1,40) sql,
sharable_mem, executions, hash_value,address
FROM V$SQLAREA
WHERE sharable_mem > 1048576 ORDER BY sharable_mem DESC)
WHERE rownum <= 10 ;
Top 10 by Version Count:
set linesize 100 set pagesize 100 SELECT * FROM (SELECT substr(sql_text,1,40) sql,
version_count, executions, hash_value,address
FROM V$SQLAREA
WHERE version_count > 20 ORDER BY version_count DESC)
WHERE rownum <= 10 ;