How to evaluate the performance of the server you need to acquire 130

The number of concurrent connections in the web system (BS) is related to the database memory.

The first is the database, which has a limit on the maximum number of connections at the time of creation. Taking Oracle as an example, the maximum number of connections supported by default is more than 100 (I forgot the exact number), and each connection will occupy a certain amount of memory. If a user requests your web page again while all connections are occupied, a connection to the database error will occur.

Generally, when a user visits your web page, each IE will occupy a number of connections, so some ** restrict users from opening the page in one IE.

The server's memory can also be throttled when teammates connect. As mentioned earlier, each connection takes up a certain amount of memory, and when there is not enough memory, problems arise. However, the memory of the current servers is generally relatively large, if you have a large number of users, you can calculate in advance how much memory is enough.

A concept related to the number of concurrent connections is that the number of users at the same time will be counted in many places. 100 connections doesn't mean you can have 100 users at the same time**, and it has a lot to do with your programming. An important concept is connection pooling (similar to the acquisition of dynamic IPs), which can support more users with a limited number of connections.

The general configuration of 1000 users should not be a problem, and it is recommended to have a larger memory!

Small applications are suitable for SQL Server, Oracle uses overkill and small use, and the speed is not as good as SQL, and when the database reaches a certain record, SQL Server will have a bottleneck, and everything is very slow, so you can only use large databases such as Oracle. (The exact number of records depends on your relevant table.)

It won't be saved'null'String bar.

select * from Order Number where **Trade No='null'

If you can find it out if you query it in this way, it means that it is a null string.

There shouldn't be the situation you said, I just tried it, no problem, you use this:

select * from the order number.

Take a look at the value in the "** trade name" field in the result, is there any value displayed as "null"?

I guess it's also a null character stored instead of a real unentered data;

What's going on? That is, when you save the data, the null is typed by yourself, and you don't let it be empty.

Don't use is null, change it to = null, if it's a character =''

Because the field is defined as a string, use single quotes.

select * from order number where innull(**trade name) false

Guess: there may be spaces near null!

There can be many reasons for this. As follows: A partition of the disk is running out of space; The amount of memory or CPU background computing is too large due to the installation of too many programs; medium virus; Poor heat dissipation. Specific issues need to be dealt with on a case-by-case basis.

There are several possibilities;

1.There is too much garbage and it has not been cleaned up for a long time;

2.The running program is too big, too many.

3.Poisoning, the most likely, it is recommended to reinstall the pure version of the system.

Shut down redundant and useless programs to conserve resources.

Is that not enough memory......

Do you mean to analyze the statement, it is related to the specific table structure, the general database itself must provide such a tool, for example, the informix database is set explain on after running the performance analysis of the sql statement will be generated into a text file, and the mysql database provides the way to explain the sql statement to view the performance of this statement, and the performance of this statement can be intuitively seen from the analysis results of explain. This allows you to optimize the database or change statements.

sqlserver can use the database engine optimization consultant, oracle doesn't know, the standard sql is about the same, you can get sqlserver optimization.

This problem of yours can be said to be not a problem, there is a reason for the slow operation of the detection, your system has been used for a long time, and you have installed a lot of things during this period of time, these things may be booted up, which will occupy your resources, the most disgusting thing is that some programs you uninstall, but the uninstallation is not clean, many processes are still running in the task manager, because they have been uninstalled, these processes will instead occupy more resources, causing you to run slowly, clean the registry, Clean up the boot startup service and close the processes that you don't need to use, and this problem will not appear.

Phenomenon: Problems with switching graphics cards, it seems that there is more than one graphics card.