First, if the prompt "Service Unavailable" appears, you can access it after a few refreshes. This happens because your website exceeds the iis limit. Because the 2003 operating system prompts IIS too much, it is not like the 2000 system prompts "excessive number of links", but the prompt "ServiceUnavailable" The situation is caused by the fact that the website exceeds the system resource limit, mainly because the program occupies too much resources. For example, the same 100-person online forum, the resources of the Leo Forum are more than 10 times the resources of the PW Forum; in addition, some infinite loop programs, or programs that are not optimized, will take up too much system resources, and the system resources are obvious. It is limited. However, the operating system of WINDOWS2003, each website runs in an independent process and does not affect each other. If a website's program occupies too many resources or too many errors occur, the system log will prompt: "The application pool 'xxx' is automatically disabled because of a series of errors in the process of serving the application pool. , or if the application pool 'xxx' exceeds its job limit setting. At this time, visit this website will prompt: ServiceUnavailable. The general system will return to normal in about 30 seconds, and it will be accessed normally after several refreshes. In addition, if your website currently has too many visitors, which exceeds the system's iis connection limit, ServiceUnavailable will also appear. If there are too many connections under the win2k host, you will be prompted: too many connections, please try again later; Win2003 host just prompt: ServiceUnavailable) Second, there is no limit to IIS connection, or encounter Service Unavailable more common in the use of ACCESS database sites generally use windows2003IIS6 users may have this problem has been normal system, suddenly there is a website can not open the prompt: ServiceUnavailable but this site does not limit the number of IIS connections. Then immediately affected other websites, and in less than a while, other websites have all become ServiceUnavailable. What is the reason? //This article from www.jb51.net we can know after analysis, or the old problem of MS. The ACCESS engine is gone. Repaired with the server doctor's file doctor, when viewing the repair results, some files will be found causing the ACCESS engine "catastrophic failure" and "the object reference is not set to the instance of the object" error. After the file doctor fixes it, the system will return to normal. Third, when browsing a Windows SharePoint Services Web site, the prompt: ServiceUnavailable1. Microsoft Internet Information Services (IIS) 6.0 does not correctly configure the application pool for the virtual server, this problem may occur. Solution To resolve this issue, follow these steps: 1. Verify that the application pool is configured for the virtual server. The default application pool is MSSharePointPortalAppPool. Follow these steps to determine which application pool the virtual server is using. a. Click “Start”, point to “Administrative Tools", and then click “Internet Information Services (IIS) Manager”. b. Expand “ServerName”, expand “Web Site", right-click the virtual server, and then click “Properties”. c. Click the “Home Directory” tab. The application pool configured for the virtual server is listed in the "Application Pool" box. d. Click “OK”. 2. Verify that the password used by the application pool account is correct. IIS does not automatically poll for password changes in the Active Directory directory service. If the application pool account is a domain account and its password has expired, you may receive the error message described in the "Symptoms" section of this article after you reassign a new password to this account. 3. Verify that the application pool account is a member of the IIS_WPG group and the STS_WPG group on the server. 4. Restart IIS to recycle the application pool ServiceUnavailable” The reason for the occurrence of ServiceUnavailable is generally insufficient resources, such as IIS, CPU or memory. All of our virtual hosts do not restrict IIS, so we can eliminate IIS. All of our server operating systems are windows2003. One of the most important things is "application pool". In general, 30-50 stations share a program pool. This program pool can be simply understood as a resource library. 30-50 stations share this resource. We limit the CPU usage of a program pool to 60% and the memory usage to 200M. If this resource is used up by one of the stations, the program pool will stop, and all stations using this program pool will have a "ServiceUnavailable" resource prompt until the program pool is restarted. In most cases, 60% of the CPU and 200M of memory are fully used; if there is a spam program or an attack, there may be a sudden increase in CPU or a large amount of memory usage. This is the reason why most of the "ServiceUnavailable" occurs. From the current situation we monitor, most of the CPU usage is between 90% and 100%. 1. What happens when "ServiceUnavailable” appears? We have independently developed a program that monitors and repairs IIS. It automatically checks IIS every 10 minutes. If it finds that the program pool is stopped, it will restart. Therefore, once “ServiceUnavailable”, no more than 10 minutes, it will be fixed automatically, in most cases only 2-5 minutes. Most other companies do not have a monitoring program, they can only be repaired by hand. The general duration is 2-6 hours to discover and start. 2, frequent occurrences "ServiceUnavailable" rd how to do? If this prompt appears frequently, it indicates that one of the stations sharing resources with you has a problem. Please contact our technician for troubleshooting. 3. Is there a server problem with "ServiceUnavailable”? Many people think that it is a problem of server instability, but it is not. If it is a server problem, the prompt of "ServiceUnavailable" will not appear, but it will be directly smashed, and even FTP will not go up. This happens because a station consumes a lot of resources, and the server's resources are always limited. If the set value is exceeded for a long time, the server will automatically stop the program pool to prevent users from affecting other program pools.