Appendix 21. Basic process for troubleshooting

Appendix 21. Basic process for troubleshooting

1.1 Connection process for clients

The client application requests a connection to the remote SQL Server server, first through the firewall and then through SQL Server authentication before the connection can be established.

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1.2 Collecting fault Information

When a client connection fails, there is usually an error message. Through these error messages, you can roughly determine which part of the fault occurred.

For example, the error message in the following example indicates that the client application could not connect to the port of the specified remote SQL Server instance.

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As another example, the error message in the following examples represents the information of logon account errors.

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Some applications may intercept and encapsulate error messages, in which case it is recommended that you first attempt to connect to the server using other client tools and get as detailed an error message as possible.

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1.3 Basic process of troubleshooting

First, you need to confirm that the SQL Server service is started. The simplest way to do this is to try to connect to the SQL Server engine by using a client-side tool (such as SSMS) locally on the SQL Server server. It is important to note that if this server has multiple instances installed, you need to confirm that the instance name that you are trying to connect to locally is consistent with the instance name used by the client.

Second, the SQL Server instance must allow the remote client to connect. If the instance has a remote connection disabled, or if the maximum number of connections is exceeded, the client connection is unsuccessful.

If the SQL Server server can connect locally and the remote client cannot connect, you need to confirm the network traffic between the server and the client. This includes DNS resolution, firewalls, network communication protocols and many other factors.

You will then also need to confirm that the client driver is installed and that the client application is matched.

Finally, verify that the user account is valid and that the password is correct.

This article from "SQLServer2014 series" blog, declined reprint!

Appendix 21. Basic process for troubleshooting