Why does the “SQL Server does not exist or access denied” error occur?
This issue is complex and can arise from various reasons, requiring multiple checks. Generally, the following possibilities exist:
1. Incorrect SQL Server name or IP address.
2. Incorrect network configuration on the server side.
3. Incorrect network configuration on the client side.
How to troubleshoot and fix the “SQL Server does not exist or access denied” issue?
To fix this issue, we generally follow these steps to identify the cause of the error.
First, check the physical network connection:
ping <server IP address/server name>
If ping <server IP address> is unsuccessful, it indicates a physical connection issue, and you need to check hardware devices such as network cards, hubs, routers, etc. Another possibility is that firewall software installed between the client and server, such as ISA Server, may block responses to ping, telnet, etc. Therefore, when checking connection issues, temporarily disable the firewall software or open all blocked ports. If ping <server IP address> is successful but ping <server name> fails, it indicates a name resolution issue. Check whether the DNS service is functioning correctly. Sometimes, the client and server are not on the same local network, making it difficult to identify the server using its name directly. In such cases, you can use the HOSTS file for name resolution. Here’s how:
1 Open the HOSTS file with Notepad (usually located at C:/WINNT/system32/drivers/etc).
Add a line mapping the IP address to the server name, for example:
172.168.10.24 myserver
2 Alternatively, configure it in the SQL Server Client Network Utility, detailed later.
Next, use the telnet command to check the SQL Server’s operational status:
telnet <server IP address> 1433
If the command is successful, you will see the screen flash, and the cursor will keep blinking in the upper-left corner, indicating that the SQL Server is working normally and listening for TCP/IP connections on port 1433. If the command returns an “unable to open connection” error, the server-side SQL Server service might not be started, TCP/IP protocol might not be enabled, or the server might not be listening on the default port 1433.
Then, check the server-side network configuration to ensure protocols like Named Pipes and TCP/IP are enabled.
You can use the SQL Server’s built-in Server Network Utility to check this:
Click Programs > Microsoft SQL Server > Server Network Utility
Open the tool, and in the “General” tab, see which protocols are enabled for the server. Generally, enable both Named Pipes and TCP/IP protocols. Select the TCP/IP protocol and choose “Properties” to check the default port settings for the SQL Server service. The default port is usually 1433. If “Hide server” is selected, clients cannot see this server through server enumeration, providing protection but not affecting connectivity.
At last, check the client-side network configuration.
You can also use the SQL Server’s built-in Client Network Utility for this:
Click Programs > Microsoft SQL Server > Client Network Utility
Open the tool, and in the “General” tab, see which protocols are enabled for the client. Generally, enable both Named Pipes and TCP/IP protocols. Click on the TCP/IP protocol and select “Properties” to check the default connection port, which must match the server’s port.
Click the “Aliases” tab to configure server aliases. The alias is the name used to connect, while the server in the connection parameters is the actual server name. They can be the same or different. Configuring aliases is similar to using the HOSTS file.
Summary
By checking these aspects, you can generally eliminate the first type of error.
