ccna levels

state to another. Therefore, when the database contains only the results of successful transaction commits, the database is said to be in a consistent state. If a database system fails in operation and some transactions have not yet been completed, some of the modifications made to the database have been written to the physical database, and the database is in an incorrect state, or an inconsistent state. 3, isolation. Execution of one transaction cannot interfere with other transactions. That

in the above example, the database is consistent on the data before and after the transfer. Isolation: If multiple transactions are executed concurrently, the result should be the same as the serial execution of multiple transactions. Obviously, the simplest isolation is the serial execution of all the transactions: first, First, and one to allow the next to execute. However, the database is inefficient, such as: Two different transactions just read the same batch of data, so it can be done con

In many cases, PHP files may encounter some very difficult-to-troubleshoot errors, such as output of large white pages. It is possible that the PHP error level shields some non-fatal errors, resulting in no error prompt. Therefore, understanding and familiarity with PHP error levels may become a new method for debugging errors.Php. by default, the PHP Error Reporting level is E_NOTICE, and E_ALL indicates reporting all non-fatal errors, because these

Differences between the levels of integrated wiring systems In general, the levels of Integrated cabling systems are divided into three types: integrated, enhanced, and basic. So what are the differences between the three types? Level 1: Comprehensive The integrated architecture is suitable for scenarios with high configuration standards in the Integrated Wiring System. It uses optical fiber cables and co

[Switch] from the perspective of the framework, five levels of PHP and their respective salary and treatment, five types of salary. [Switch] looking at the five levels of PHP and their respective salary and treatment from the framework, I accidentally saw this article and was somewhat touched. I started my blog and used it to motivate myself. In the original article, [transfer] The framework shows the five

The chrome version of Angry Birds has been upgraded! This new version of 1.2.0 adds checkpoints designed for Christmas and the highly destructive mighty eagle on the iOS platform. Including: For 42 levels, you can use mighty eagle to play the game again. You need to pay $0.99. There are 25 season's greedings levels, and only one level can be played every day until the last level is displayed on Jan

SQL server lock mechanism (I)-Overview (lock types and ranges) SQL SERVER lock mechanism (II)-Overview (Lock compatibility and lockable resources) This article introduces the locking mechanism of SQL SERVER (iii) -- Overview (lock and transaction isolation level) Vi. Impact of various transaction isolation levels Users who modify data will affect other users who read or modify the same data at the same time. That is, these users can access data con

During the interview, you may often ask "what do you want to do in the next five years ?", This may be a difficult question to answer. In China, the answer may generally be team leader, Manager, ect, specialist, etc. In China, you may think that manager will be the programmer's next goal, but abroad, managers and programmers may be two different branches. The superior ect or specialist is better than the manager, because these people have higher IQ requirements. There was such an article on the

Cocos2d-x 3.2 Monopoly game project development-Part 5 standalone game-levels choose ScrollView, monopoly Standalone Click MenuScene. cpp to call Director: getInstance ()-> pushScene (MapChooseScene: createScene ()); Go to the level selection interface. We use the ScrollView control to create this interface. Because the position of the scrollview is relatively random after being dragged, I think it is to drag it to the second image to display the

1. Runs 64-bit registers and is compatible with the armv7 architecture software. That is, it supports both 32bit and 64bit, aarch64 aarch32 2. the privilege and mode are separated, and armv7 is integrated. In armv8, there are pl3, PL1, pl0, and no pl2 in the security status, and the safe memory space can be accessed. In the unsafe state, there are pl2, PL1, pl0, and no pl3, and the safe memory space is not accessible. Each PL level determines a set of commands and registers. 3. Exception

sea of ridicule in front of the leadership, and dress yourself as a technical master. It is really difficult to introduce the confused office culture into the technical department! Level 10: I am a dumb or dumb. If I write a SELECT statement, I will say that I am proficient in oralce. If I don't even know a few registers, I will say that I understand Assembly. I suggest sending all the registers to Japan as IT industry workers, earning money from the Japanese is also a serious blow to the Ja

Introduction: This tutorial is mainly for beginners, and the author explains how to use channels to handle the color levels and sharpness of pictures through examples. A friend sent me a picture and asked me how to get the color levels back and do a little bit sharper. Open the picture a look, sure enough color level is very weak, the petals are not clear. But this kind of picture has the same feature: it

Staff often need to analyze and summarize large amounts of data stored in Excel to discover trends and implications of data. For example, in the Sales Performance table shown in Figure 1, how do you quickly show how each employee's sales compare in 1 ~ March? Figure 1 Sales Performance table The "Levels" feature of Microsoft Office Excel 2007 enables you to quickly understand the distribution trend of your sales data by taking advantage of co

transaction read data that was not committed by another transaction. (There is a lot of potential for concurrent processing of the system) 2. Non-repeatable reading Within the same transaction, when reading the same data multiple times, the data was found to have been modified by another committed transaction. (data that is read two times within a transaction is not the same.) ） 3. Phantom Reading A transaction executes a query based on the same query criteria, and the returned record contains

Label:Access levels Modifier Class Package Subclass World Public Y Y Y Y Protected Y Y Y N No modifier Y Y N N Private Y N N N The following table shows where the members of the Alpha class is visible for each of the access modifiers that can

that was just made. Now the line read by T2 is invalid. ) exp: Xiaoming's score was 89, and transaction a changed his score to 98, but transaction A was not yet committed. at the same time, transaction B is reading Xiaoming's score, reading to Xiaoming's score is 98. then, transaction A to the exception and rolled back the transaction. Xiaoming's score rolled back to 89. finally, transaction B reads the data for Xiaoming with a score of 98 as dirty data, and transaction B makes a dirty read

Detailed description and comparison of the four transaction isolation levels of MySQL, and detailed description of mysql Detailed description and comparison of the four transaction isolation levels of MySQL At the SQL: 1992 transaction isolation level, InnoDB is REPEATABLE READ by default ). MySQL/InnoDB provides all four transaction isolation levels described in

exactly what they are and what they are connected to.What is a "cascading context"cascading contexts (stacking context) is a three-dimensional concept in HTML. In the CSS2.1 specification, the position of each box model is three-dimensional, which is on a flat canvas and X轴 Y轴 represents a cascade Z轴 . In general, elements areOn the page along the X轴Y轴 tile, we don't notice the Z轴 cascading relationships on top of them. Once the element is stacked, it can be found that an element might overwrit

)Isolation is when multiple users concurrently access the database, such as when the same table operation, the database for each user-opened transactions, can not be disturbed by the operation of other transactions, multiple concurrent transactions to be isolated from each other. To achieve this effect: for any two concurrent transactions T1 and T2, in the case of transaction T1, the T2 either ends before the T1 starts, or starts after the T1 ends, so that every transaction does not feel that an

speak.Isolation (Isolation): In general, changes made by an office are not visible to other transactions until they are finally submitted. Notice here that the "usual", behind the transaction isolation level will be said.Durability (persistent): Once a transaction commits, its modifications are persisted to the database. When the system crashes, the modified data is not lost. (There is also a relationship between persistent security and the refresh log level, which corresponds to different