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You can configure the server's technical options, including the number of maximum simultaneous requests, listen queue size, and DNS usage.
To get the number of simultaneous requests, the server counts the number of active requests, adding 1 to the number when a new request arrives and subtracting 1 when a request is finished. When a new request arrives, the server checks to see if it is already processing the maximum number of requests. If it has reached the limit, it defers processing new requests until the number of active requests drops below the maximum amount.
You can set the number of maximum simultaneous requests, which is the number of active requests allowed for the server at one time. If your site is processing many requests that take many seconds, you might need to increase the number of maximum simultaneous requests. However, for general Internet or intranet use, you probably will not need to change the default value (128 requests).
If you need to change the number of maximum simultaneous requests, set the number before starting the server.
From the Web Manager home page, click Enterprise Web Server servername > Server Preferences > Performance Tuning.
In the Maximum Simultaneous Requests field, enter the number of requests.
Click OK > Save and Apply.
You can configure the server to use Domain Name System (DNS) lookups during normal operation. By default, DNS is not enabled; if you enable DNS, the server looks up the hostname for a system's IP address. Although DNS lookups can be useful for server administrators when looking at logs, they can affect performance. When the server receives a request from a client, the clients's IP address is included in the request. If DNS is enabled, the server must look up the hostname for the IP address of each client that makes a request.
IMPORTANT: If you turn off DNS lookups on your server, hostname restrictions won't work and hostnames won't appear in your log files. Instead, you'll see the IP addresses.
You can also specify whether to cache the DNS entries. If you enable the DNS cache, the server can store hostname information after receiving it. In the future, if the server needs information about the client, the information is cached and available without further queries. You can specify the size of the DNS cache and an expiration time for DNS cache entries. The DNS cache can contain from 32 to 32768 entries; the default value is 1024 entries. Values for the time it takes for a cache entry to expire can range from 1 second to 1 year (specified in seconds); the default value is 1200 seconds (20 minutes).
To modify DNS settings, do the following:
From the Web Manager home page, click Enterprise Web Server servername > Server Preferences > Performance Tuning.
Select No or Yes to enable DNS.
Select No or Yes to enable Async DNS.
Select No or Yes to cache DNS entries.
(Conditional) If you cache DNS entries, enter the number of entries that you want cached in the Size of DNS Cache field. In the Expire Entries field, enter the number of seconds at which a cache entry will be deleted.
Click OK > Save and Apply.
The listen queue size is a socket-level parameter that specifies the number of incoming connections the system will accept for that socket. The default setting is Incoming Connections.
Normally, you should not change the listen queue size. The default setting is sufficient in most cases.
If you manage a heavily used Web site, you should make sure your system's listen queue size is large enough to accommodate the listen queue size setting from the Server Preferences form. If you do change the listen queue size, make sure that your system supports the new size. The listen queue size set from the Server Preferences form changes the listen queue size requested by the server. If the server requests a listen queue size larger than the system's maximum listen queue size, the size defaults to the system's maximum.
IMPORTANT: Setting the listen queue size too high can degrade server performance. The listen queue size was designed to prevent the server from becoming overloaded with connections it cannot handle. If your server is overloaded and you increase the listen queue size, the server will only fall further behind.
To modify the listen queue size, do the following:
From the Web Manager home page, click Enterprise Web Server servername > Server Preferences > Performance Tuning.
In the Listen Queue Size field, enter the listen queue size you want.
Click OK > Save and Apply.
With HTTP 1.1, a connection can be set to be persistent (similar to Keep Alive in HTTP 1.0). However, even if a connection is persistent, it still needs to have a time-out setting or it might consume system resources.
Normally, you should not change the persistent connection time-out. The default setting is sufficient in most cases.
From the Web Manager home page, click Enterprise Web Server servername > Server Preferences > Performance Tuning.
In the HTTP Persistent Connection Time-out field, enter a number (representing seconds).
Click OK > Save and Apply.
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