Querying features from an ArcIMS service layer
Querying map features can range from retrieving a list of attributes by clicking a feature on the map using the Identify tool to running advanced analytic models using geoprocessing. The ability to perform the various kinds of query tasks depends on the type of server and the type of service you are using. For example, ArcIMS Feature services stream feature data to ArcMap, which allows you to use most querying functionality available in ArcGIS for Desktop. However, since the other services send images, the range of querying functionality against these services is more limited.
Query restrictions are listed in the Data Source text box for each ArcIMS service layer.
ArcIMS reports all point features as geometry type multipoint for Feature, Image, and ArcMap Server services. If you are trying to perform a task that does not work on multipoints, you will not be able to perform this on an ArcIMS service.
ArcIMS Feature services stream vector features to ArcMap. ArcMap holds feature geometry and feature IDs in memory, but feature attributes are not held to minimize memory use. You can perform many of the same querying operations against ArcIMS feature services that you would a shapefile or geodatabase feature class. For example, you can
- Identify features.
- Find features.
- Select features (interactively, by attribute, by location).
- Use feature services as input to geoprocessing tools.
To improve performance, you may want to use the feature cache when working with ArcIMS feature services.
Image and ArcMap Server services
When you query against an ArcIMS Image service or an ArcMap service, the server sends information back to ArcMap in a binary format. This information contains attribute data for the features you are querying and may also include feature geometry. However, in many cases, the server administrator does not want to pass along feature geometry and may choose to exclude it from the query results. In this case, the Source tab on the Layer Properties dialog box will display the message Query Results: Do not include geometry.
When feature geometry is unavailable, certain ArcMap functionality will be disabled when interacting with Image or ArcMap Server services.
Tasks that are supported when query results do not include geometry
- Using the Identify tool
- Using Select By Attributes
- Using the Find dialog box
- Drawing a selection*
- Changing selection color*
Tasks that are unsupported when query results do not include geometry
- Performing geoprocessing tasks
- Buffering with the Buffer Wizard
- Flashing features from Identify or Find results
- Creating a bookmark from Identify or Find results
- Selecting features based on location
- Creating a selection layer
- Changing the selection symbol
- Zooming to features based on selection or Find results
- Panning to features based on selection or Find results
*When the service layer does not include feature geometry, ArcMap relies on the server to draw the selected features. This requires two separate image requests to the server: one to draw all the features of the service that are currently visible and the other to draw only the selected features. To draw the selected features on top of the nonselected features, the image type returned from the server must support transparency; otherwise, the image returned for the selection will obscure all other service features. If the server disables all output types that support transparency (GIF, PNG, PNG8), ArcMap will not render the selection. You can still select features and view the selection in the sublayers attribute table. You just won't see the selection rendered in the map.
Access restrictions and forbidden requests
Some services have constraints on query operations. You can view this restriction on the Source tab on the Properties dialog box.
To keep the ArcIMS server running effectively and efficiently, a server administrator can enable a time-out on the server. A time-out is the maximum amount of time the server is given to respond to a given request. Once the time-out value is exceeded, the ArcIMS server will stop processing the request.
The majority of ArcIMS servers set a time-out value sufficient for the server to respond to most requests. If you do make a request that times out, you should receive an error message. If this happens, you will need to amend your request for the server to process it.
ArcIMS server administrators can limit the number of features returned to clients. Feature limits can be placed on individual ArcIMS services. The feature limit affects all ArcGIS query functionality, including the Identify and Find tools and any geoprocessing. If you suspect incomplete results when using ArcIMS services, you may want to contact the service administrator to see if a feature limit has been set.
Image and ArcMap services and feature limits
ArcIMS Image and ArcMap services are a bit different with regard to feature limits. Since ArcMap is receiving an image and not streamed vector data, all map features are displayed regardless of the feature limit.
The feature limits affect the number of records returned for an attribute table as well as the number of features returned in a query. This can produce unexpected results. For example, when the feature limit is 10, even though all the features display in the map, a maximum of 10 records will be returned from each query, even though many more features match the query. For instance, there are 42 states whose population is greater than 1,000,000, but only 10 would be returned due to the feature limits.