In a Nested Loops Join, for example, the first accessed table is called the outer table and the second one the inner table. In a Hash Join, the first accessed table is the build input and the second one the probe input. Stream Aggregate and Merge Joi…

1. Not so long time ago, I got a report from customer. It's reported that they had a report getted very slow and finally throw an error. I finded fout the problem sql in source code and excuted it in sql managment studio. It costs 1 minute and 46 sec…

为什么需要SQL Profile Why oracle need SQL Profiles,how it work and what are SQL Profiles... 使用DBMS_XPLAN.DISPLAY分析SQL执行计划,通常会看到Note中有类似下面这样的提示: Note ----- - SQL profile "SYS_SQLPROF_0158283a9b920000" used for this statement SQL profile由人为手工创建或在Automa…

sql tunning advisor 使用的主要步骤: 1 建立tunning task 2 执行task 3 显示tunning 结果 4 根据建议来运行相应的调优方法  下面来按照这个顺序来实施一遍:    1  建立测试表以及索引 SQL> CREATE TABLE test_sql_advisor AS SELECT OWNER,OBJECT_NAME,OBJECT_ID FROM DBA_OBJECTS; Table created SQL> select count(*) fro…

This artical is forcused on Oracle 11g Release 2.  It is an summary from the OCP documentation. The topics discussed here including tunning memory, tunning sql, tunning segment access, identifing objects that are invalid or unusable and using Databas…

advisor调优工具优化sql(基于sql_id) 问题背景:客户反馈数据库迁移后cpu负载激增,帮忙查看原因 解决思路:1> 查看问题系统发现有大量的latch: cache buffers chains 等待:latch:cache buffers chains出现的原因 1.不够优化的SQL. 大量逻辑读的SQL语句就有可能产生非常严重的latch:cache buffers chains等待,因为每次要访问一个block,就需要获得该latch,由于有大量的逻辑读,那么就增加了latc…

建议不使用(*)来代替所有列名 用truncate代替delete 在SQL*Plus环境中直接使用truncate table即可:要在PL/SQL中使用,如: 创建一个存储过程,实现使用truncate命令动态删除数据表 create or replace procedure trun_table(table_deleted in varchar2) ascur_name integer;begincur_name:=dbms_sql.open_cursor;dbms_sql.parse(c…

2014-08-16 Created By BaoXinjian…

永无止境的调优 service level agreements: 是一个量化的调优的指标. performance 只要满足业务OK就可以了, 没必要调的很多, 因为有得必有失, 一方面调的特别优化, 可能导致另一方面出问题 主要还是关注SQL调优把(Troubleshooting Oracle performance 这本书主要是针对SQL的调优) 调优是告诉你怎么样使用ORACLE 没有1本书能大而全的论述性能调优 database administrators 和 system admi…

--创建 dbms_sqltune.create_tuning_task ; --执行 dbms_sqltune.execute_tuning_task; --产看创建的task 和 status SELECT TASK_NAME, STATUS   FROM DBA_ADVISOR_LOG D   LEFT JOIN USER_ADVISOR_TASKS U D.TASK_NAME = U.TASK_NAME  WHERE D.TASK_NAME = 'TASK_NAME'; --显示调优结果…