by index

DbFileSequentialRead in the top 5 of AWR recently occupies a very large percentage of time. Generally, this waiting event is normal. However, there are some problems with the current system performance. The concurrency is large and slow. Therefore,

Index misunderstanding in oracle Learning We all know that indexes can increase the speed to eliminate sorting, but they are often abused in actual use, which not only wastes resources, but also plays a negative role. This error is often invisible

The index and index of the partition technologyAbout Partitioning technology-Index  I. Partition Index classification: Local prefix partition index) Global partition Index) Local non-Prefix partition index (localnon-prefixed partitioned index) 1.1

New Features of Oracle11g: invisibleindex (invisible index) How do you feel if a table has more than a dozen indexes? Obviously, it will slow down the process of adding, deleting, and modifying data. Do not expect developers to build indexes. My

Tag: Data key binding functionThe data () function has two parameters, the first one is bound, and the second parameter specifies the order of the bindings. It is often used when the data needs to be updated.By default, the data () function binds

Several methods for obtaining an oracle execution plan: 1.set autotrace onI believe this method is the simplest and most commonly used method. This method is often used to analyze an SQL statement. Here the syntax is pasted, which is simple: SQL>

Reproduced original address: http://www.cnblogs.com/lhj588/archive/2012/01/06/2314181.htmlFirst, install the XLRD moduleDownload the HTTP://PYPI.PYTHON.ORG/PYPI/XLRD module installation to the Python website, provided the Python environment is

Today is. I was planning to mix the direction key index and other indexes into other index logs, but I still feel that this part is too important. Record the arrow key index notes here. What is a direction key index? The direction key index is also

Now we know how the optimizer reacts to these technologies and clearly shows the best applications of bitmap indexes and B-tree indexes. Now we know how the optimizer reacts to these technologies and clearly shows the best applications of bitmap

Create your own oracle interpretation plan and oracle interpretation plan   1. Explain the plan When an explain plan is used to generate an expected execution plan for a query, the output includes the following: Each table accessed by SQL; Method

High-performance index policiesCreating a correct index and using it properly play a key role in the query performance. We have introduced the capabilities and weaknesses of various indexes. The following describes the power of indexes. There are

Array: Create a new array. Array_walk: Allows the User-Defined Function to process every element in the array. Arsort: Sorts the values of an array from large to small. Asort: Sorts the values of an array from

The NLS_COMP and NLS_SORT parameters are sorted by binary by default, which is inappropriate for Chinese sorting, for example. Use these two parameters to specify the sorting method, such as pinyin or, which may cause performance problems. The

This document describes how to use SQL Plan Management to manage SQL Execution plans. SQL Plan management provides components for capturing, selecting, and evolving SQL Plan information to prevent performance degradation caused by sudden changes in

In the actual optimization work, it is an important method to change the full table scan of the large tables in the execution plan into an index scan. When tuning a large table, it is inevitable to try to create an index, this is not very good. It

An invisible index is ignored in the OPTIMIZER_USE_INVISIBLE_INDEXES unless you manually set the OPTIMIZER_USE_INVISIBLE_INDEXES initialization parameter to TRUE at the session or system level. Mark An invisible index is ignored in the OPTIMIZER_USE_

Execution Plan related to B-tree indexesUnique index scan, index range scan, full index scan, quick full index scan, and skip index scan. Unique index scan: SQL> create table employee(gender varchar2(1),employee_id number);Table created.SQL> insert

Mysql optimization Summary (1) I. SQL _mode mode of mysql: (1) This mode means that the SQL mode can control server operations, and the SQL mode exists at the global and session level. If you want to know the current value of global or session-level

This article is mainly for everyone to bring a cliché in PHP data structure: DS extension. Small series feel very good, now share to everyone, also for everyone to make a reference. Follow the small series together to see it, hope to help everyone.

The reverse of the PHP array in an article, "How to sort php arrays," we introduced the sort, asort, and Ksort, which are sorted in ascending order of the array, so if you want to implement the reverse of the arrays? Here's another set of functions