Understanding and Implementing ArcSDE By Timucin Bakirtas GIS Developer & Research Associate, MERI/CIMIC 2002

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Understanding and Implementing ArcSDE

By

Timucin Bakirtas

GIS Developer & Research Associate,

MERI/CIMIC

2002




















Understanding and Implementing ArcSDE



This proposal, prepared for the MERI/GIS will describe how to manage spat
ial Database.
ArcSDE is a way of managing spatial data in a database management system. It allows
you to manage geographic information in one of four commercial databases. IBM DB2,
IBM Informix, Microsoft SQL Server, and Oracle, and ESRI's file
-
based data
with
ArcSDE for coverages


ArcSDE provides the infrastructure required managing multiple users editing the same
spatial database with long transactions, alternate versions. It allows GIS data to be
directly maintained in the format of spatial types support
ed by the DBMS vendors.
ArcSDE provides the business logic software for not only creating simple geometric data,
but also technology for supporting advanced GIS data types such as images, networks.


ArcSDE plays a fundamental role in a multi
-
user GIS. Wit
h ArcSDE, Our ArcGIS soft
wares such as ArcInfo? ArcEditor? ArcView? GIS, and ArcIMS? Can work directly with
spatial data managed in our RDBMS. ArcSDE also works as an application server,
delivering spatial data to many kinds of applications and serving sp
atial data across the
Internet.









The application can connect directly to the RDBMS without using the ArcSDE
application server. Connecting to the ArcSDE application server provides performance
advantages as well as providing a mechanism for suppor
ting server side applications.
Direct connections provide an easier way to achieve RDBMS connectivity with less
administration. You can, for example, directly connect to an Oracle Spatial database
without requiring the ArcSDE application server. Direct con
nections are also an
advantage in configurations requiring fail over support. The connection configuration
options allow you to define the system that best supports your needs.


The spatial data representation is built upon standard data types in the RDBMS
. In cases
where the RDBMS has extended spatial data types, ArcSDE can access and use these
types for managing feature geometry. When necessary, ArcSDE provides the mechanism
for managing feature geometry. These storage methods provide a fast and compact
r
epresentation for spatial data.


With ArcSDE, we can move data from one RDBMS to another without loss of
information through ArcSDE data export and import capabilities. This is especially
important if your enterprise has a heterogeneous database environmen
t, possibly
including work group or personal database systems. This capability is available for even
the most advanced geodatabase designs.

ArcSDE defines a logical model for spatial data, implemented on top of a physical
database representation. Applicati
ons developed with the ArcSDE API will run, with
little or no change, on different physical schemas within an RDBMS. This lets the GIS
database administrator choose the best database schema for each individual dataset to
meet the requirements of an applica
tion. For example, one dataset can be maintained and
edited using a binary schema, stored as LONG RAW in Oracle, while another dataset
might be stored as Oracle Spatial geometry types. How the data is stored is transparent to
the end user application.

ArcS
DE manages the integrity of the point, line, and polygon information added to the
database and won't allow ill
-
formed feature geometry to be inserted for example, polygon
boundaries must be closed. In addition, you can use the ArcSDE gateway with ArcInfo t
o
implement additional integrity constraints on the data model that aren't practical to
implement in the RDBMS itself. For example, you can add connectivity rules for utility
networks.

We can significantly reduce the cost of building and maintaining a spat
ial database by
using ArcSDE with ArcGIS. ArGIS provides many tools and datasets to help us quickly
implement your application
. ArcSDE can work with a RDBMS to store and retrieve data.
Fetching features for a map window and using the attribute constraint.
Fetching features
and projects them on the fly and processing this geocoding requests.




ArcSDE for Raster Data:

A raster is a rectangular array of equally spaced cells, which taken as a whole represent
thematic, spectral or pictur
e data. Raster data can represent everything from qualities of
land surface such as elevation or vegetation, to satellite images, scanned maps, and
photographs. Images such as TIFF, JPEG, and GIF can be rendered by internet browsers.
These rasters are comp
osed one or more bands. Each band is segmented into a grid of
square pixels. Each pixel is assigned a value that reflects the information it represents at a
particular position. ArcSDE stores raster datasets similar to the way it stores a geometry
object.
A raster column is added to a business table and each value of the raster column
contains a reference to a raster stored in a separate raster table. Therefore each row of a
business table references an entire raster. Applications build on the basic SDE Ras
ter
support to provide raster maps or catalogs of raster images.



What is the difference between ArcSDE for Coverages versus ArcSDE?



ArcSDE for Coverages allows you to serve your
shapefile, coverage, LIBRARIAN

and
ArcStorm data to client software such a
s ArcIMS in the manner of ArcSDE. Your data
does not reside in ArcSDE but is merely served by the ArcSDE for Coverages software.
Performance will be similar to displaying your data in Arcplot with Defined Layers.
ArcSDE for Coverages is intended to be a br
idge product to allow you to serve your
legacy data to clients’ applications such as ArcIMS that cannot read coverage data.
ArcSDE for Coverages can also serve shapefiles and ArcIMS can read shapefiles directly
so there is less of a need to use it to serve

them. With ArcSDE for an RDBMS, the data is
maintained within the SDE tables. Performance will be much better than with ArcSDE
for Coverages.
TCP/IP access is used; there is no need for NFS. Client access is extended
to all ESRI data formats
ex: MO access

to ArcStorm layers.
Applications developed now
can be re
-
used when migrating to ArcSDE for RDBMS;
SQL and INFO syntax will be
different.







Basic Advantages of using ArcSDE:


1
-
)
Powerful benefits from Relational Database Manage
ment Systems (RDBMS)

-

Leverage scalable architecture

2
-
) Integrated data model

-

Store GIS and tabular data together

-

Coordinated transactions

3
-
) Scalable, robust system architecture

-
A server
-
side application data server in 3
-
tier

system architecture (
ArcSDE
server acts an application server for GIS clients.)

-

An application
-
side software component in 2
-
tier system architecture (

Client
uses ArcSDE component for direct access to RDBMS.)

4
-
) Multi
-
user access Geodatabase technology

-

Take advantage of f
eature intelligence

-

Facilitates data sharing

5
-
) Performance tuning

-

Minimizes network traffic with server
-
side data filtering, performance can be
faster



6
-
) Industry Standards, Support for Windows and Unix

-

Client and server

-

Conforms to Open
GIS Feature Specifications

-

Has open, documented architecture and APIs

7
-
) Modern networking solution

-

Uses TCP/IP protocol



Why should not We Use ArcSDE?


Billions of dollars are spent worldwide annually to construct and maintain these spatial
database
s. Leveraging these vast data holdings is a challenge. Today, we need to provide
access to all of our data. Our Spatial database, which are raster images, coveragases,
shapefiles are increasingly integrated in corporate information systems. To provide open

access to our spatial databases we need ArcSDE.



What are the requirements for ArcSDE what we have available and what we need?


Version: 8.2

DBMS:
Oracle 8i (32 bit)


Platform: PC
-
Intel Windows 2000


1
-
) A PC
-
Intel Windows 2000 installed with enough disk

space in this case.



-

Typical installation for
Oracle8
i
Enterprise Edition, 530 MB

-

Typical installation for ArcSDE 8.x
4 MB.



2
-
)
SP 1 (optional), SP 2 (optional), SP3 (optional)



4
-
) A licensed DBMS Software (Oracle 8.x or 9.x)


3
-
) A licensed Arc
SDE Software.


5
-
)
Simple TCP/IP, Network Card or Microsoft Loopback Adapter
.










REFERENCES:


http://www.esri.com/software/arcgis/arcinfo/arcsde/index.html


http://arconline.esri.com/arconline/sysreqs.cfm?PID=3


http://support.esri.com/


http://forums.esri.co
m/forums.asp?c=2


http://www.esri.com/library/presentations/understanding_arcsde.pdf


http://w
ww.esri.com/library/brochures/pdfs/arcsde
-
raster.pdf