Using ArcCatalog

Geodatabases
Geodatabases are relational databases that contain geographic
information. Geodatabases contain feature classes and tables.
Feature classes can be organized into a feature dataset; they can
also exist independently in the geodatabase.
Feature classes store geographic features represented as points,
lines, polygons, annotation, dimensions, and multipatches and
their attributes. All feature classes in a feature dataset share the
same coordinate system. Tables may contain additional attributes
for a feature class or geographic information such as addresses or
x,y,z coordinates.
Many objects in a geodatabase can be related to each other. For
example, tables containing customer addresses and billing
information are related, just as state and county feature classes
are related. To explicitly define the relationships between objects
in a geodatabase, you must create a relationship class. Relationships
let you use attributes stored in a related object to symbolize,
label, or query a feature class.
Feature classes in a feature dataset can be organized into a
geometric network or a topology. A geometric network combines
line and point feature classes to model linear networks—for
example, electrical networks—and maintains topological relationships
between its feature classes. A topology is a set of relationships
that define how the features in one or more feature classes
share geometry—for example, cities must be properly inside
states.
Creating and accessing geodatabases
To manage your own spatial database, you can create a personal
geodatabase. If you do this, your data will be stored in a
Microsoft Access database. For a multiuser spatial database, use
ArcSDE, which lets many people in an organization simultaneously
update data stored in a centrally located RDBMS. SDE ®
for Coverages lets you access coverage, ArcStorm, or ArcInfo
Librarian databases just as you would an RDBMS.
You can access personal geodatabases directly in ArcCatalog,
but to access data stored in an RDBMS you must add a database
connection. To do so, double-click one of the Add Database
Connection wizards in the Database Connections folder. You’ll be
prompted for information such as your username and password
and the database to which you want to connect.
In general, when you create a database connection, you choose
the data provider that will retrieve your data from the database.
For multiuser spatial databases, ArcSDE is the data provider.
Object Linking and Embedding Database (OLE DB) providers
generally retrieve nonspatial data only. You can preview these
tables in ArcCatalog and join their values to spatial data. If an
OLE DB provider can retrieve spatial data and present it in Open
GIS Consortium, Inc. (OpenGIS ® or OGC), format, you can
preview that data in the Catalog.
All database connections are stored in the Database Connections
folder by default, but they can be moved elsewhere. For example,
you can place a connection that has read-only access to the
database in a shared folder where others can access it; they can
use it to view the database’s contents in the Catalog without
having to know the details of how to connect to the database.
The first time you select a database connection, ArcCatalog tries
to connect to the database. If the connection attempt is successful,
ArcCatalog will list the items contained in the database. When
you see a little red x on the database connection’s icon, it is
disconnected; until you have reestablished the connection, you
can’t access data stored in the database.
Items in an RDBMS are owned by the user who created them.
When ArcCatalog lists the contents of an ArcSDE geodatabase,
the owner’s name appears before the item’s name. For example, a
feature class named valves that is owned by the user admin
would appear in the Catalog as admin.valves. If the RDBMS
supports databases, such as SQL Server, the database name
will appear between the owner’s name and the object’s name.
56 USING ARCCATALOG