In the process of using SQL Server, the most common problem users encounter is the failure of the connection. In general, there are two ways to connect SQL Server, one is to take advantage of SQL Server's own client tools, such as Enterprise Manager, Query Analyzer, transaction Profiler, and so on, the second is to use the user's own development of client programs, such as ASP scripts, VB programs, client programs are using ODBC, or OLE DB, to connect to SQL Server. Next, we'll talk about how to solve the problem of connection failure in terms of these two ways of connecting.
One, client tool connection failed
When you connect to SQL Server with SQL Server's own client tools (for example, in Enterprise Manager), the most common errors are as follows:
1. SQL Server does not exist or access is denied
ConnectionOpen (Connect ())
2, user ' sa ' login failed. Reason: not associated with a trusted SQL Server connection.
3, timeout has expired.
Here's how to solve the three most common connection errors in turn.
The first error "SQL Server does not exist or access is denied" is usually the most complex, the cause of the error is more, there is more to be examined. Generally speaking, there are several possibilities:
1, the SQL Server name or IP address spelling error;
2, server-side network configuration is incorrect;
3, the client network configuration is incorrect.
To solve this problem, we generally follow the steps below to find out the cause of the error step by step.
First, check the network physical connection:
Ping < server IP address >
Or
Ping < server name >
If ping < server IP address > failure, indicating a physical connection problem, this time to check hardware devices, such as network cards, HUB, routers and so on. Another possibility is that the firewall software is installed between the client and the server, such as ISA server. Firewall software may block the response to Ping, Telnet, and so on, so when checking connectivity problems, we have to temporarily shut down the firewall software or open all the blocked ports.
If ping < server IP address > Success and ping < server name > failed, there is a problem with name resolution, so check to see if the DNS service is working properly. Sometimes the client and the server are not in the same LAN, it is very likely that the server name can not be used directly to identify the server, at this time we may use the Hosts file for name resolution, the specific method is:
1, use Notepad to open the Hosts file (usually located in C:\WINNT\system32\drivers\etc).
2, add an IP address and server name of the corresponding records, such as:
172.168.10.24 MyServer
It can also be configured in SQL Server's client Network Utility, which is described later.
Second, use the Telnet command to check the working status of the SQL Server server:
Telnet < server IP address > 1433
If the command succeeds, you can see the cursor flashing in the upper-left corner after the screen flashes, indicating that the SQL Server server is working properly and listening for TCP/IP connections on port 1433, and that the server side does not start SQL if the command returns an error message "Cannot open connection" Server service, either the TCP/IP protocol is not enabled on the server side or the server side is not listening on SQL Server's default port 1433.
Current 1/5 page
12345 Next read the full text
