Contents of a coverage workspace

A coverage is stored in the computer as a directory. The directory name is the coverage name. An organized collection of coverages is called a workspace. The following are some limitations on the coverage names:

• Cannot be longer than 13 characters
• Cannot contain spaces
• Cannot start with a number
• Does not have an extension
• Must be in all lowercase letters

A coverage is composed of a set of files, each of which contains information about a particular feature class. The set of files stored in a coverage varies depending on the feature classes present in a coverage. For example, the illustration below shows a workspace that contains a number of coverages. The directory structure and files contained in the coverage, soils, are shown below. Note that this coverage contains polygon features and an annotation subclass, type.

Each coverage workspace has an INFO database stored under a subdirectory, info. Each .adf file in a coverage folder is related to a pair of the .dat and .nit files in the INFO folder. The arc.dir file in the INFO directory is used to keep track of which pair of .nit and .dat files is related to which .adf file.

Note:

Never delete the INFO folder, because that will corrupt your coverage.

The contents of a coverage file appear differently in ArcCatalog than they do in Windows Explorer. Below you can view the contents of a coverage in ArcCatalog. The states coverage is contained in the Yellowstone workspace. The INFO folder in the workspace is not visible in ArcCatalog. The arc.adf file in the states folder is represented in ArcCatalog as the arc feature class in the states coverage.

The following table summarizes the main set of files used to store each coverage feature class. For each feature class, the common files used by ArcGIS to manage the spatial information are listed.

This is not a complete list of the files used to store a coverage. However, knowing which files are used is not as important as knowing which feature classes are present in a coverage and the geographic phenomena they represent. As a general rule, only the records in feature attribute tables are directly accessible to the user. Other files are stored in binary format and are automatically maintained by ArcGIS.

Feature class	Spatial data in coverage directory	Feature attribute table coverage directory	Feature attribute table in INFO database
Point	lab.adf	pat.adf	.nit and .dat
Arc	arc.adf	aat.adf	.nit and .dat
Node	arc.nit, arc.adf	nat.adf	.nit and .dat
Route	arc.adf, sec.adf	<route>.rat	.nit and .dat
Section	arc.adf	<route>.sec	.nit and .dat
Polygon	pal.adf, cnt.adf, lab.adf, arc.adf	pat.adf	.nit and .dat
Region	rxp.adf, <region>.pal	<region>.pat	.nit and .dat
Annotation	<anno>.txt	<anno>.tat	.nit and .dat
Tic	tic.adf	tic.adf	.nit and .dat
Link	lnk.adf	lnk.adf	.nit and .dat
Coverage extent	bnd.adf	bnd.adf	.nit and .dat

Coverage feature class files and extensions

Note that text in angle brackets (<>) refers to user-assigned names for the coverage or feature class. Use your operating system command for listing coverage file names.

It is important to note that if a coverage is not copied or deleted using ESRI software options, such as ArcCatalog or an ArcToolbox geoprocessing tool, it will not be copied or deleted correctly. Never copy a coverage using Windows Explorer; otherwise, your data will be corrupted.