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to select the crosstab (intersection table) as the underlying table, which is the table referenced by the other table.Like what: The EMP table description describes the intersection of the location table and the category table. SELECT * FROM location
L,
CATEGORY C,
EMP E
WHERE e.emp_no between, and
e.cat_no = C.cat _no and
e.locn = L.LOCNwill be more efficient than the following SQL: SELECT * from
EMP E, location
L,
CATEGORY C
WHERE e.cat_no = c.cat_no and
e.locn = L.
monitoring is necessary 207Thinking on the construction of 6.7 operation and maintenance platform--meta data management 2096.8 Monitoring blind spots and diagnostic cases 210Monitoring blind spots: A potential monitoring problem caused by dual 210Diagnostic Case: Standby CPU Usage Exception Optimization 213Diagnostic Case: Two alarm information combined with analysis of DG Problem 216Diagnostic case: Monitoring anti-monitoring error--an analysis of a Orabbix alarm 222Diagnostic case: Customizin
first wait event is read by other session.
Top 5 Timed Foreground Events
Read by other session is defined as follows:
Read by other session Definition: When information is requested from the database, Oracle will first read the data from disk into the database buffer cache. if two or more sessions request the same information, the first session will read the data into the buffer cache while other sessions wait. in previous versions this wait was clas
For some distributions today, there are already three dynamic performance views available to DBAs (database Administrator, DBA) and developers, respectively, V$sql, V$sqlarea, and V$sqltext.
These views can be used to collect statistical information about the execution of SQL commands. The fourth dynamic performance view, V$sqlstats, is added to Oracle 10g, Rele
This technical article, provided by the International Oracle User Group (IOUG), is a user-organized organization that enhances the level of Oracle database experts and database developers by providing high-quality information, training, networking, and support. This article picks up the "Predictable Oracle Application Perform
In order to be successful, I'll involve some preliminary steps that will be needed to see what happens, including running Plustrce SQL scripts, creating a Explain_plan table, granting roles, configuring Sql*plus environments to view execution plans. All of these steps include "use automatic tracking in Sql*plus" In Oracle 9i R2 Database Performance Tuning
Summary of Oracle Performance Tuning recommendationsPrinciple One: Note the connection order in the WHERE clause:Oracle uses a bottom-up sequential parsing where clause, according to which the connection between tables must be written before other where conditions, and those that can filter out the maximum number of records must be written at the end of the WHERE
Buy Oracle Database Course package and enjoy 85 discount!!Package Address: http://edu.51cto.com/pack/view/id-807.htmlPerformance optimization for Oracle 11g R2 databaseDatabase performance problem is the most discussed topic in database field, because it involves database principle, IO storage, server performance, fore
Tags: process optimizer consolidation requires merging auto overwrite session accessThe full execution order of the SELECT statement:The full execution order of the SQL SELECT statement: 1. The FROM clause assembles data from different data sources; 2. The WHERE clause filters the record rows based on the specified criteria, 3, the GROUP BY clause divides the data into multiple groupings, 4, uses the aggregation function for the calculation, 5, uses the HAVING clause to filter the grouping; 6, e
"Performance Tuning" Oracle AWR reporting metrics full resolution
What is AWR?
=====================================================================================================
AWR (Automatic workload Repository)
A bunch of historical energy data, placed on the Sysaux table space, AWR and Sysaux are all 10g, are the key features of
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, usually, if the statement can avoid the use o
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 = ' President 'OR job = ' MANAGER ' GROUP JOB hav
Friends who are interested in this course can add my QQ2059055336 and contact me.This course focuses on Oracle RAC architecture and how it works, understanding and mastering the relevant technologies under the RAC database, such as cache Fusion, Failover, load balance, FAN, OCR, and voting disk. Through the implementation of the VMware virtual environment, the installation and deployment of RAC database, the daily
Oracle is a high-performance database software. The user can adjust the parameters to achieve the optimization of performance. Performance optimization is mainly divided into two parts:
First, the database administrator through the adjustment of system parameters to achieve the goal of optimization;
The second is tha
Tags: implementation mechanism originally page organizes tables based on free article content index ClustFollowing the book on SQL tuning (SQL tuning or SQL optimization) in the essentials of high-performance SQL tuning and case resolution, we talk today about one of the most important core mechanisms of SQL
, Microseconds_per_second ms_per_sec, pct_of_time pct from Opsg_delta_report where Microseconds_per_second > 0; Monitoring the usage of indexes: With In_plan_objects as(SELECT DISTINCT object_name from V$sql_plan WHERE object_owner = ' SCOTT ')SELECT table_name,Index_name,CaseWhen object_name was NULL then' NO 'ELSE' YES 'END as In_cached_planFrom User_indexesLeft OUTER JOIN in_plan_objectsOn (index_name = object_name);4. Identify the SQL statements that benefit from the binding variab
valuable, while the Oracle lock mechanism is more advantageous, allowing Oracle applications to be more comfortable with DML operations, but this does not mean that you can do whatever you do, and in reality, even a lot of senior developers, are not very understanding of the characteristics and application of Oracle transactions, so often unnecessary use of manu
Linux system tuning authoritative guide, linux tuning Guide
1. Disable SELINUX.1.1 modify the configuration file to make SELINUX disabled permanently effectiveSed's # SELINUX = enforcing # SELINUX = disables # G'/etc/selinux/config ==> restart the system to take effect1.2 temporarily disable SELINUX[Root @ hadoop01 xni
. Net Performance Tuning Series
Article
Index of series articles
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