WebGIS development practice manual 2.2 ArcIMS server component [2]

2.2.3. ArcIMS Service

Whether it is a space server or virtual server, the ultimate goal is to generate and manage the ArcIMS service. The ArcIMS service is the key to the external map release of ArcIMS, it is also an interface for communication between the client and the GIS server.

One or more different types of ArcIMS services can exist on one server. As shown in area 2, 6, there is an image-type ArcIMS service san:

Figure 2 zhang6 existing ArcIMS service san

With the ArcIMS administrator tool, we can create four types of ArcIMS services: Image Service, ArcMap image service, Feature Service, and metadata service. Because different services meet different access requirements, has different settings.

Image service is our most common ArcIMS service. It returns the map content to the client in the form of JPEG, PNG, or GIF images, each new request generates a new image file on the server.

Oracle map image service is a special image service. Its map configuration file is mxd or PMF data generated by ArcMap or arcreader.

Ø feature service is a service that publishes map content through element streams. Element streams are a temporary compression format that exists only when the client is open. This type of service is required if you want to use the Java client, WFS connector, ArcMAP, arcreader, editnotes of ArcIMS, or local data.

The metadata service can publish the data information of a dataset, that is, metadata. The metadata of geographic data describes the content, quality, type, data composition, and spatial location of the data.

2.2.4. Space server instance

Each space server contains one or more instances (an instance is essentially a thread). It is the most basic processing unit of the ArcIMS space server. Generally, each virtual server is assigned two instances (one process contains two threads), but the only exception is the ArcMap image server, with only one instance at a time.

As we can imagine, the number of instances is equivalent to the number of requests that ArcIMS can simultaneously process. For example, if a space server has two image instances, it can only process map requests of two image services at a time. If there are more requests, you can only wait in queue for the processing of the server instance in the application server.