ArcGIS之空间索引

http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?id=2059&pid=2057&topicname=Setting_spatial_indexes

Setting spatial indexes设置空间索引

Spatial indexes in personal geodatabases

Whenever you create a feature class in a personal geodatabase, whether with the New Feature Class wizard, a geoprocessing tool, or any other method, you must specify a grid size or accept the default grid size of 1,000. Once a feature class is created, the grid size cannot be modified. Since the grid size is permanent, ArcGIS does not automatically recalculate its size at the end of certain operations as it does with file and ArcSDE geodatabases. 

Keep in mind that the default size of 1,000 is specified in the units of the feature class's coordinate system. This means if your feature class is in a geographic coordinate system and you use the default, all features will be placed in a single grid cell. This will provide no benefits to performance. 

If you suspect a poor grid size is causing slow performance, you can try reloading the data to a new feature class with an optimal grid size: 

1. Use the Calculate Default Spatial Grid Index geoprocessing tool to find a good grid size for the feature class. This tool outputs up to three optimal grid sizes. You will use the Default Spatial Grid Index 1 value in the next step.
2. Create a new, empty feature class with the New Feature Class wizard. In the wizard, specify the same coordinate system and fields as in the feature class you're reloading (the wizard allows you to import these). When you get to the list of fields, click on the Shape field and, for the Grid 1 property, specify the new grid size. Proceed to complete the wizard.
3. Use the Append geoprocessing tool to import all records from the source data to the new, empty feature class.