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How To: Improve redraw speed for features of a theme

Summary

When working with a very large shapefile, zooming in closely on a set of features improves the redraw speed only slightly, or doesn't seem to improve at all.

Procedure

Redraw speed can be improved by creating a spatial index on the themes in the view.

· A spatial index is automatically created, if one doesn't already exist, when you do a spatial join or a theme-on-theme selection.

· You can create a spatial index by using the Avenue request 'BuildIndex' on any coverage feature source.

· You can create a spatial index in ArcInfo with the INDEX command. ArcView will use that index.

You can determine whether a feature data source contains an index by using the Avenue request 'HasIndex'.

· You can also create a spatial index from the ArcView interface:
1. Open the theme's table.
2. Make the Shape field active.
3. Select Create Index from the Field menu.

If the menu only shows a Remove Index option, a spatial index already exists for that theme/coverage.


With a spatial index present, once you zoom in to a large scale portion of the view, the redraw only occurs on the features actually in the View window itself.

Note:
Creating a spatial index writes two files (*.sbn and *.sbx) to the directory containing the source shapefile.