tuning oracle sql queries

Tags: tabs Other applications ABS SSE contains increased data process structure understandingThe parameters of the tuning function in the Oracle database system are called initialization parameters, and the database administrator needs to properly adjust these initialization parameters to optimize the Oracle system according to the actual situation.1 introduction

. The customer provided an AWR report during peak hours. After careful analysis, it was found that it was a high-CPU-consuming SQL statement, which only took 85% of the CPU, this gives us an in-depth understanding of SQL optimization. We have also done some DB optimization before, basically through analysis tables, index creation, parameter adjustment, PATCH, and so on. However, this time, it lasted for a w

Kernel.shmmaxKernel.shmmax = 2147483648[Email protected] ~]# sysctl-p[Email protected] ~]# su-oracle[Email protected] ~]$ sqlplus '/as sysdba 'Sql*plus:release 10.2.0.1.0-production on Mon Nov 16 05:50:00 2009Copyright (c) 1982, 2005, Oracle. All rights reserved.Connected to:Oracle Database 10g Enterprise Edition Release 10.2.0.1.0-productionWith the partitionin

, and this performance is affected. So in view of this, we often do the optimization method is: The association to use clustered index (uniqueness) as far as possible We know that this algorithm assumes that both tables are sorted, so when we apply it, it is preferable to use the sorted table Association. If there is no sort, also the associated item to select is the index overlay, because the sorting of the large table is a resource-intensive process, and we choose to sort the index overlay

Io is very relevant, when the free buffer waiting in the v$session_wait of the entry is very small or not, Explain the DBWR process of your system will be enough, do not need to adjust, there are many items of free buffer wait, your system must feel very slow, then your DBWR is not enough, the resulting wio has become your database performance bottlenecks, the solution is as follows: A.1 to increase the write process while adjusting the db_block_lru_latches parameters Example: Modify or add the

The following articles mainly describe the ultimate SQL Performance tuning Technology of DB2, including the impact of pointers on the Performance of DB2 databases, DB2 performance tuning technology and a detailed description of more future tuning technologies, the following is the main content of the article. DB2,

GROUP BY:Increase the efficiency of the group BY statement by filtering out unwanted records before group by. The following two queries return the same result but the second one is significantly faster.Copy CodeThe code is as follows:Low efficiency:SELECT JOB, AVG (SAL)From EMP GROUP job has job = ' president ' and AVG (SAL) >xxxEfficient:SELECT JOB, AVG (SAL)From EMPWHERE JOB = ' President 'OR job = ' MANAGER ' GROUP JOB having and AVG (SAL) >xxx7,

are very readable6. Use where to replace having (if possible)Optimize GROUP BY:Increase the efficiency of the group BY statement by filtering out unwanted records before group by. The following two queries return the same result but the second one is significantly faster. Copy the code code as follows: Low efficiency:SELECT JOB, AVG (SAL)From EMP GROUP job has job = ' president ' and AVG (SAL) >xxxEfficient:SELECT JOB, AVG (SAL)From EMPWHERE JOB = '

the deterioration of performance is a variety of factors, and sometimes the results of the performance degradation caused by multiple elements, this requires the database administrator has a more comprehensive computer knowledge, can be sensitive to the impact of the database performance of the main reason. In addition, good database management tools are also important for optimizing database performance. Database performance optimization tools commonly used in

Document directory Preliminary steps Using bind variables There are several relatively easy steps you can take to improve performance. From the user's perspective, one of the most frequently used interfaces with a database involves SQL statements, so getting a handle on them is a good place to start, in terms of being able to see an immediate improvement. -->Oracle

SQL Server Performance Tuning 3 (Index) MaintenanceHeat1 reviews Brook Stream GrassSQL Server Performance Tuning 3 (Index) MaintenanceObjectiveThe previous article describes how to improve the query performance of a database by building an index, which is really just the beginning. Subsequent to the lack of proper maintenance, the index you created earlier can e

Speaking of the tuning of SQL Server, I think everyone would like to know this knowledge. I am also exploring the way, we have any good ideas, welcome to discuss and study. Win the people's long, can avoid weaknesses. This article is mainly from the programmer's SQL code, if you want to read, you can download the Internet to read (of course, the best way to buy

a single processing record. Try to use an explicit cursor (CURSORs). With an implicit cursor, two operations will be performed.10. Use larger buffer (e.g. 10MB, 10,240,000) to increase the speed of export and import11. Alias for use table when you concatenate multiple tables in an SQL statement, use the alias of the table and prefix the alias to each column. This reduces the time to parse and reduces the syntax errors caused by column ambiguity.12. I

Tags: des style blog http color using strong AR dataBackgroundMySQL and Oracle were used before, and there was not much use for SQL Server. Recently, due to project reasons, to read the database of other projects, take out a gate of the switch history, and the other side of the use of SQL Server, so the study of SQL Se

Label:Original: SQL Server database Performance tuning tipsThe reasons for the slow query are many, and the following are common: 1. No index or index is not used; 2, I/O throughput is small, forming a bottleneck effect; 3, insufficient memory; 4, the network speed is slow; 5, the amount of data queried is too large; 6, lock or deadlock; 7, the return of unnecessary rows and columns; 8, query statement is n

. server.2005. Technical Insider "series Conclusion This article first to this bar, short, easy to understand, this article mainly introduces the query plan of the joint operators, the next we analyze SQL Server parallel operations, in multicore hyper-threading gathered today, see SQL How server uses parallel operations to maximize the use of existing hardware resources to improve performance, is inte