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Working with the map cache

Release 9.3
Last modified September 11, 2008
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About working with the map cache

If you're working with data stored in a geodatabase or from an ArcIMS feature service, building the map cache can often speed up common ArcMap tasks. The map cache allows you to temporarily store the features in the current map display in ArcMap to your local machine's memory. Because retrieving the features from local memory is a fast operation, using the map cache will often result in performance improvements.
The map cache only stores features in geodatabases and ArcIMS feature services, so no data from rasters, coverages, shapefiles, or other types of services is cached. The map cache is most useful when you will be working within a specific area of a map.
For example, if you are working with data in an ArcSDE geodatabase that serves features over a network, features in the current extent must be retrieved from the source database each time your display is updated. Building a map cache, however, can reduce the load on your network and the geodatabase since ArcMap accesses this information from your computer's random access memory (RAM). Since features are cached on the client, it reduces the number of queries the client needs to execute on the server.
Some of the activities that can often benefit from a map cache include drawing large or complex datasets, labeling, editing, selecting features, retrieving the same features for multiple layers on a map, and drawing features using a definition query. Labeling, for example, can be a slow and costly process, requiring multiple round-trips to the data source as the label engine attempts to place the maximum number of labels on the map.
Learn more about labels


Using the map cache tools

ArcMap has tools to help you build and work with the map cache. These tools are found on the Map Cache toolbar. You can create a map cache by clicking the Build Map Cache button Build Map Cache button. You can also use the automatic cache (auto-cache) function to automatically update the map cache whenever you move outside the currently cached extent.
The auto-cache can be useful if you are going to be working in a series of different geographic areas and you don't want to rebuild the cache for each area. It is also convenient when you don't know the exact boundaries of the area you want to cache.
Since auto-cachemay hinder performance, you should set an auto-cache minimum scale. A map cache will be created automatically unless the map is zoomed out beyond the minimum scale. For example, suppose you set 1:50,000,000 as the minimum scale. When the map is zoomed in to 1:14,500,000, the map cache will be created automatically, but when the map is zoomed out to 1:75,000,000, the map cache will not be rebuilt.


Maximizing the map cache's performance advantages

For geodatabase data, the advantages of the map cache are most pronounced when the data source is an ArcSDE geodatabase. In a multiuser environment, consistent use of the map cache in ArcMap can significantly improve the overall performance of the system by reducing the number of queries to the geodatabase, the number of features retrieved from the geodatabase, and the overall network traffic. Care must be taken, though, when using map caches to edit in multiuser, nonversioned edit sessions.

In addition, there may be a minor performance gain with a map cache for file or personal geodatabases such as when editing features with large numbers of vertices or accessing the data over a network.

When working with ArcIMS feature services, the map cache can also help reduce traffic to the server. ArcIMS image and ArcMap Server services are not supported by the map cache.

Whether you are using geodatabase or feature service data, the map cache is most useful when you will be working within a specific area of a map. Work that requires frequent panning and zooming across a large area will not usually benefit from a map cache.

Learn more about the map cache and nonversioned editing


How to work with the map cache

Adding the Map Cache toolbar

Click View, point to Toolbars, and click Map Cache.
The Map Cache toolbar appears.


Building a map cache

  1. Pan or zoom to the area on the map where you want to work.
  2. Click the Build Map Cache button Build Map Cache button on the Map Cache toolbar.
  3. The features in the current extent are held in memory locally.

Tips

  • Because the Map Cache is stored in your computer's RAM, building a cache for a large area with many features may consume a large amount of memory and can take some time. You can cancel building the map cache by pressing the Esc key.
  • You can quickly return to your map cache extent at any time in your ArcMap session by clicking the Zoom To Map Cache button Zoom to Map Cache button on the Map Cache toolbar.
  • You can click the Show Map Cache button to see the extent of the current cache. You are using the map cache only when the Show Map Cache button is green Green Show Map Cache button. If the button turns red Red Show Map Cache button, it means you are partially outside the map cache's extent and no longer using the map cache. If the button is unavailable Unavailable Show Map Cache button, you are completely outside the cached area.
  • If any part of your current display extent is outside the cached area, you are no longer using the data cached on your computer. To use the map cache again, you'll need to build a new cache, use auto-cache, or return to the cached extent.
  • To empty the map cache, click the Empty Map Cache button Empty Map Cache button on the Map Cache toolbar.
  • When working with a map cache while editing, the rules for Stop Editing are: if edits are saved, the map cache is maintained; if edits are not saved, the map cache is cleared. If the edit operation is aborted, whether it is on Stop Editing or within the current edit session, the map cache is cleared.


Setting the auto-cache minimum scale

  1. Zoom out just beyond the scale at which you'll be working.
  2. Click the Set Auto-Cache Scale button Set Auto-Cache Scale button on the Map Cache toolbar.

Tips

  • You can turn off the auto-cache when you begin working at a fixed display extent and are no longer moving around the map.
  • When you move around the map and are still within the cached extent, the cache is not rebuilt. When the display extent is not completely within the cache, the cache will be rebuilt, provided your map is not zoomed out beyond the minimum auto-cache scale.
  • To avoid inadvertently building an auto-cache of your whole geodatabase, set a minimum scale for the auto-cache. The auto-cache won't be rebuilt if you zoom out beyond the minimum scale.


Setting auto-cache options

  1. Click View and click Data Frame Properties.
  2. Click the Map Cache tab.
  3. Check Automatically create map cache to use the auto-cache.
  4. Check the Set minimum scale for auto-cache box.
  5. Type a minimum scale in the box or click the Use Current Scale button to set the current scale as the minimum scale.
  6. Click OK.


Clearing the auto-cache minimum scale

Click the Clear Auto-Cache Scale button Clear Auto-Cache Scale button on the Map Cache toolbar.


Seeing the extent of the cached area

Click the Show Map Cache button on the Map Cache toolbar.
The currently cached area will flash on the map.

The currently cached areas is flashed



In the example, the area outside the rectangle is not within the current cache extent, so the Show Map Cache button would be red.
-Optionally, if you plan on working at this extent, click the Build Map Cache button to build a new cache or click the Auto-Cache button to use the auto-cache.

Tips

  • The Show Map Cache button is enabled only when you have built a map cache and your map's current extent intersects the extent of the map cache.
  • If any part of your current display extent is outside the cached area, you are no longer using the data cached on your computer. To use the map cache again, you'll need to build a new cache, use auto-cache, or return to the cached extent.
  • You can quickly return to your map cache extent at any time by clicking the Zoom to Map Cache button Zoom to Map Cache button on the Map Cache toolbar.

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