1. WFM 6202: Remote Sensing and GIS in Water Management
[Part-B: Geographic Information System (GIS)]
Lecture-4(b): Geo-Database
Akm Saiful Islam
Institute of Water and Flood Management (IWFM)
Bangladesh University of Engineering and Technology (BUET)
December, 2008

2. Lecture Topic Understand basic Geodatabase concepts and structure
Know the advantages in using the Geodatabase format
Managing a GeoDatabase
Creating GeoDatabase

3. First Generation Storage/Linking
AS400
Database
Access
Tabular Data
Spatial Data
Tabular/Spatial data is linked outside the database
Links occur using unique IDs….Parcel Numbers
Storage is still in separate locations

4. Second Generation Storage/Linking Geodatabases
Tabular Data
Spatial Data
Tabular/Spatial data is stored/linked in a single location!!

5. Benefits of a GeoDatabase
Spatial & attribute data integrity
Intelligent Behavior
Centralized Data Storage
Increased Performance
Advanced Analysis Capabilities
Multi-user editing (SDE format)

6. Benefits of Migrating to a Geodatabase Data Integrity
Maintain tabular data more efficiently
Reduce typological data errors
Maintain spatial data more efficiently
Reduce spatial errors
Pro-West & Associates

7. What is a Geodatabase? A spatial and attribute data container
Relational database management system (RDBMS)
Maintains data integrity
Apply Rules and Behavior
Native data format for ArcGIS
Relational Database - A method of structuring data as collections of tables that are logically associated to each other by shared attributes. Any data element can be found in a relation by knowing the name of the table, the attribute (column) name, and the value of the primary key.

8. 2 Types of Geodatabase Personal Geodatabase Enterprise Geodatabase
Stand alone PC, MS Access database
Supports individual and small groups on moderate size datasets
Enterprise Geodatabase
Exists on underlying RDBMS through Spatial Database Engine (SDE) e.g. SQL Server
Usually runs on a dedicated server
Supports many users and massive datasets
Supports raster datasets

9. Two types of GeoDatabases
Personal
Access
Multi-user
SDE
GIS
SQL
SDE
Data Storage
Interpreter
View/Analyze
There are two types of GeoDatabases: Personal and Multi-user.
A Personal Geodatabase uses Microsoft Access as the DBMS (Database Management System) which has certain limitations imposed by Access and limitations imposed by ArcGIS. It is a great learning tool, but may fall short of expectations due to some limitations listed later. All Personal GeoDatabases created with earlier (than 8.3) software should be upgraded to version 9.1. This is easily done within the Properties for the GeoDatabase.
A Multi-user Geodatabase uses one of the supported DBMS’s listed below. It requires an SDE license and has the full suite of capabilities outlined in this chapter and more.
As information is presented in this chapter, differences between the two will be pointed out.
Supported DBMS’s (hardware platforms may differ):
IBM DB2 Universal Database (UDB)
INFORMIX Dynamic Server
Microsoft SQL Server
Oracle

10. The Personal Geodatabase It’s not Scary!
Stores spatial and tabular data in an Access database format
Sets the stage for future SDE geodatbase migration
Edit in ArcView, ArcEditor or ArcInfo

11. Geodatabase Features
Feature Dataset
Contains tables, feature classes, feature datasets, topology rules, etc.
Topology
Feature Classes
Tables

12. Geodatabase Elements Geodatabase Feature data set Geometric network
Feature class
Relationship class
Table
Annotation class

13. GeoDatabase (GDB) structure
Stores
Feature datasets
Feature classes
Tables
Raster
More
A unique structure within the GDB
One might make the statement that we can store about any type of data for our GIS needs within a Geodatabase. For the most part that is true, as long as we differentiate between the “Personal Geodatabase” and the “Multi-User Geodatabase”. As mentioned earlier, the Personal Geodatabase makes use of MS Access to store the structured tables and their relationships needed to represent our GIS data. MS Access has limitations and prohibits the storage of certain data formats (for example, Rasters cannot be stored internally with the Personal Geodatabase due to size limitations).
Because of these differences between personal and multi-user Geodatabases, one should consider the needs of the organization to determine the use of the system in setting up and choosing the RDBMS and how it will be part of the integrated system.
The common structures you will work with in the beginning are: Feature Datasets, Feature Classes, Tables and Rasters. Certainly there are other objects that are available in a Geodatabase which you should learn as you advance. Each of the basic objects will be discussed on the following pages.

14. Feature Dataset Contains Feature Classes Required for Topology
Must have same coordinate system
Required for Topology
Behavior relationships between feature classes.

15. GDB Objects: Feature Dataset
A collection of feature classes
Environment for spatial reference
Environment for topology
Environment for coincident geometry and linked annotation
Feature classes inherit spatial reference
Data loaded are
projected on the fly,
if necessary
The feature dataset provides the user with the “framework” to organize logical collections of Feature classes (even different feature types – point, line, poly) together to represent the behavior and topologic relationships that the individual Feature classes share. The extent of the flexibility delivered in using Feature datasets is much more exhaustive and efficient than in previous models, such as coverages. Feature datasets are “user grouped” Feature classes (which are discussed on the next page). This allows the user to more accurately and efficiently model real world entities as “feature groupings” and establish topological relationships between those Feature classes that participate in the topology. All of this is accomplished as a structured collection of tables in the RDBMS, thus exploiting the performance benefits of the database.
The Feature dataset name can be interpreted as the “container” for the groupings of the Feature classes listed “below and indented” under the Feature dataset.
Benefit can be reaped from having a spatial reference defined for the Feature dataset so when new Feature classes are loaded into an existing Feature dataset, the data will “project on the fly” (if necessary) into the spatial reference of the Feature dataset.

16. Feature Class Stores a single feature type
Point, Line, Polygon
Can be standalone or member of a Feature dataset
Feature Dataset
Feature Class
Stand Alone

17. GDB Objects: Feature Class (FC)
A collection of features
Each feature class has one geometry type (point, multi-point, line, polygon)
Can be stored in a
feature dataset or
‘stand-alone’
Attributes are
stored with
coordinate data
in one table
A Feature class is a collection of features. Features are vector data (which you learned in an earlier chapter as discrete x,y coordinates) and represent points, lines, or polygons.
Feature classes can be “stand alone” or be grouped into Feature datasets to model more complex topologic relationships.

18. Spatial Reference
In setting up the Spatial Reference, ArcGIS provides a dialog allowing the user to select from a standard list of coordinate systems, import from other datasets already having a Spatial Reference defined, create a new coordinate system with all the particular parameters (which is tedious and difficult), or modify an existing coordinate system. The Spatial Reference also defines the maximum spatial extent for the data.
Other parameters of the Spatial Reference for the Geodatabase are:
X/Y Domain – The “bounding rectangle” or extent of the feature class or feature dataset. It is specified with the minimum X value, minimum Y value, maximum X value, and maximum Y value.
Z Domain – The maximum range of “Z” values for the data. For example: 0 to (Sea Level to a peak of ft maximum elevation)
M Domain – The maximum range of Measure units (this can be time or distance ranges). This tolerance is also the only exception to the rule regarding consistency; feature classes within the same feature dataset can have different Measure domains. A

19. Coordinate domain Extent of available coordinates
Min and max X,Y coordinates
Precision = storage units per map unit
Example, 1000 mm per meter
Make sure it covers study area
Allow for growth
ArcCatalog default
Import: data plus room for growth
Set your own
Import from existing data
Type in extent for study area
Coordinate domain:
Spatial domain is best described as the allowable coordinate range for x,y coordinates. Precision describes the number of divisions per one unit of measure. A spatial reference with a precision of 1 will store integer values, while a precision of 1,000 will store one thousandth of a unit.
The spatial domain for a feature class or feature dataset cannot be changed. If the required x-, y-, m-, or z-value ranges for your database increases, the data has to be reloaded into feature classes with a spatial reference that accommodates the new domain.
You must store your coordinates at a specific precision. For best results, ensure that the chosen precision will support the accuracy of your data. The ArcCatalog loading wizard will look at your data and determine defaults for your precision and database growth. Naturally, it is impossible for ArcCatalog to understand your intentions, so the default settings often are not the best choice. It is important that you understand domains.
The geodatabase stores coordinates as a 4-byte integer that has a maximum value of 2,147,483,648. You decide what the units represent. For instance, if you need to store meter accuracy, then you have 2.1 billion meters to work with. If you decide to store centimeters, you would have 2.1 billion centimeters to work with. These are called storage units. You should set your storage units based on your accuracy..
Map units are the measurement units of your data, and have nothing to do with accuracy. They are the units that represent measurements. For example, the meter is the standard unit for UTM data, while the foot is the standard unit for a state plane coordinate system.
2.14 billion storage units

20. Domain
A property of a feature dataset or feature class (cannot change once set)
The domain of the feature coordinates is, essentially, the minimum and maximum ranges available for feature values, for feature classes, and for feature datasets. The exception is the Measure Domain for feature classes in a feature dataset. Feature classes in a feature dataset may have different Measure Domains.
The Feature Coordinate domains are set up upon creation of the data in ArcCatalog. All data that will be loaded in the future will have to adhere to the valid domains.
The precision of a domain will affect the extent of that domain. The spatial domain for a feature class or feature dataset cannot be changed once it is established. Here is a very short list of example precisions and the corresponding x/y domain:
Note: Precision does not have to be base 10 numbers, although this is easiest to understand.
Precision
Min. Value
Max. Value 1
2,147,483,645
1000
2,147,483,645,000 10
214,748,364.5
100
21,474,836.45

21. Domains Spatial Attribute Range of values (e.g., 0-100)
Coded values (e.g., 1 = potatoes 2 = wheat)
Briefly describe the different types. Most have been used in basic GDB already.
Coded values is new use
Recall, data type must match between the domain and the attribute where the domain is going to be implemented
Why use a domain????? [BRAINSTORM]

22. The Spatial Domain
The Geodatabase stores all geometry coordinates as positive integers
Faster Display, Processing, and Analysis
Better Compression (DBMS only)
Efficient for managing topologic relationships
Limited to 2,147,423,647 storage units.
2.14x109 meters, or miles, or inches, or ...

23. Accuracy and Precision
Accuracy in the Data
Scale of source map scale will determine accuracy*
1:600 (1”=50’) ± 1.7 feet
1:1,200 (1”=100’) ± 3.33 feet
1:2,400 (1”=200’) ± 6.67 feet
1:4,800 (1”=400’) ± feet
1:24, ± feet
Precision
Ability to store the accuracy
Significant digits
Single precision 6-7 precise digits
Double precision precise digits
Geodatabase 0-10 precise digits
Accuracy
The quality of the source document used for data automation (the map) must be taken into account for the desired level of accuracy for the user applications. Accuracy can be thought of as the “correctness” of the data – is it at the correct x/y location?
Precision
Precision can be thought of as the ability to store the accuracy of the data. If the data is highly accurate +/- 1.7 feet, the Geodatabase units must store at least 1 foot as the unit of measure. The Precision, as the GDB makes use of it, is a “multiplier” to provide digits of precision after the decimal place for the coordinates. All GDB values are in Integer, but with the multiplication being applied “behind the scenes” and transparent to the user.
Coordinate offset
If you find that your coordinate domain range is adequate to support the precision desired, but either the x or y values are exceeding the 2,147,483,648 maximum, a shift can be applied to account for the limitation. This shift is determined by finding the center of your coordinate system and accounting for the offset. Calculating the shift and scale establishes the precision and storage of the data in the GDB, and once the data is loaded, you will never directly interact with the numbers again – all work will be done in floating point numbers (as in the source data).
The shift calculation gets beyond the intended scope of this class. For the purposes of the exercises, defaults are taken for the precision once the coordinate domain is set for a specific state.

24. Example: Spatial Domain
All GIS Features Must Fit Within this Positive, 32-bit Integer Space.
OFF LIMITS
2,147,423, ,147,423,647
0 0
The Database’s Spatial Domain

25. Standard Fields Feature classes have default fields
ObjectID – unique identifier
Shape – contains coordinates of feature
Area – automatically calculated and maintained for polygons
Shape_Area (Personal GDB)
Length – automatically calculated and maintained for lines and polygons
Shape_Length (Personal GDB)
Part of the structure for every feature class attribute table are the “standard fields”. Users should view these fields as “maintained by the software”.
Many operations we perform with ArcGIS modify the geometry of the spatial data. Whether we are “slicing and dicing” land polygons or road lines, or merging and reshaping features in an edit session; geometric coordinates are often modified as we continually manage our geographic data.
Polygons, for instance have area and length properties. As we would hope, when we edit a polygon feature, the software will update the affected polygon area and perimeter.
The Shape field, though visually on our screen lists the type of geometry by name (polygon, polyline, point) actually stores the X and Y coordinates needed to represent the feature being tracked by the specific record in the database. This “blob” (binary large object) of coordinates can handle non-contiguous features such as multi-part polygons, and linear routes with gaps.
Beyond the “standard fields”, additional fields added to the feature class are said to be “user defined”.

26. Spatial Reference Property of a feature class or feature dataset
Components
Coordinate system
Coordinate domain
Permanent after definition is saved
Warning: it may look like you changed the coordinate system, but you can’t and don’t try. It messes things up!
See next slide for more information
Map features represent real world objects (entities like streams, roads, etc.). The positions of the objects on the earth’s 3-D surface are measured in geographic coordinates (latitudes and longitudes). Latitudes and Longitudes are not uniform units of measure. In remedying this measurement problem, data is transformed from 3-D coordinates into 2-D projected coordinates. By converting from geographic referenced coordinates to projected coordinates, we can easily represent one or two spatial properties (of four) accurately:
Shape, Area, Distance, or Direction
No coordinate system represents an accurate system for all four properties at the same time.
Users should choose a coordinate system that maintains the properties that are most important to their business. Once determined, the Coordinate System can be stored in the Spatial Reference for feature classes, feature datasets, and the overall Geodatabase. A performance “boost” is realized when all data is in the same Spatial Reference, plus it makes it nice when loading data into the Geodatabase having a coordinate system defined – ArcGIS will “project on the fly” to load the data into the Geodatabase coordinate system.

27. Storing Feature Coordinates
Two important considerations when storing
feature coordinates in a Geodatabase:
All data is stored as positive, 32-bit integers (Spatial Domain)
All data must maintain a Coordinate Precision.

28. Coordinate Precision
The geodatabase converts all coordinates into 32-bit Storage Units.
Storage Units are the smallest measurable unit that can be stored in a Geodatabase.
Precision is used to convert coordinate system units into storage units.

29. Example: Coordinate Precision
Precision is a Scale Factor
Used to preserve decimal places before rounding
Larger precision preserves more digits
Floating Point Coordinate in ArcGIS
( )
Multiply by Precision × 1000
Divide by Precision ÷ 1000
Integer Storage Unit in a Geodatabase (123456)
X = Precision =1000

30. Example: Precision Preservation
Coordinate System Units Precision
Storage Units =
Coordinate system units ÷
Precision =
Storage units
Meters
100
1 cm
1000
1 mm 50
2 cm
Feet 12
1 inch

31. Topology Objects Maintain data integrity Feature Dataset required
Within feature class
Between feature class
Feature Dataset required
Functionality
Display Topology Errors
Select and Correct Errors
Validation
Regarding map features, topology is relationship between features connectivity and adjacency.
Geodatabase topology provides tools to ensure integrity of spatial data.

32. Selected Topology Rules
25 available topology rules
2 Rules currently applied
Must Not Overlap
Must Not Have Gaps

33. File Management Compacting the Personal Geodatabase Procedure
Reduces file size
Procedure
In ArcCatalog, right click on the .mdb file
Select the Compact Database option in the context menu

34. Reference Data Locations
Proscribed by the Standard for Geospatial Dataset File Naming
Standard folder structure on shared f: drive
Geodata – top level geospatial data folder
Local Geodata Administrators have authority to create, delete, and change folders, but only as outlined in the standards document.

35. Data Management File Naming Standards
The current standard has 23 common geospatial dataset categories such as soils that consist of 1 or more geospatial datasets.
<disk drive>:
geodata
plants
<geospatial dataset category (directory / folder)>
soils
<geospatial dataset category (directory / folder)>
There have been several standards developed regarding many facets of the GIS Implementation. One of these is the Standard for Geospatial Dataset File Names.
The objectives of this Standard are to help in managing geospatial data by establishing directory (folder) and file naming conventions to support a nationally consistent set of core geospatial data. This will provide a foundation on which to build customized business applications such as the Customer Service and Wetland Toolkit and the Soil Data Viewer. Nationally fielded applications will be developed that rely on a consistent set of geospatial data. These applications will rely on the integrity of the data in meeting the specifications in this Standard. It is recommended that applications built locally for a Service Center or for data that is acquired locally should also adhere to these standards.
Another reason to comply with this file and directory naming convention is to organize this data at the Service Center so that it is accessible, maintainable and updateable.
It also provides guidance on the directory structure and file naming for locally acquired and derived geospatial data.
The latest version of this standard is provided as a MSWord document on this CD-ROM.
soil_a_ks057
<geospatial dataset>
soil_p_ks057
<geospatial dataset>
soil_l_ks057
<geospatial dataset>
topographic_images
<geospatial dataset category (directory / folder)>

36. Data Management File Naming Standards cont.
Elements of a file name
Location: Alpha or numeric FIPS code
soil_a_ks057
Feature category
Feature type: a-polygon, l-line, p-point, t-table, i-image, etc.
There have been several standards developed regarding many facets of the GIS Implementation. One of these is the Standard for Geospatial Dataset File Names.
The objectives of this Standard are to help in managing geospatial data by establishing directory (folder) and file naming conventions to support a nationally consistent set of core geospatial data. This will provide a foundation on which to build customized business applications such as the Customer Service and Wetland Toolkit and the Soil Data Viewer. Nationally fielded applications will be developed that rely on a consistent set of geospatial data. These applications will rely on the integrity of the data in meeting the specifications in this Standard. It is recommended that applications built locally for a Service Center or for data that is acquired locally should also adhere to these standards.
Another reason to comply with this file and directory naming convention is to organize this data at the Service Center so that it is accessible, maintainable and updateable.
It also provides guidance on the directory structure and file naming for locally acquired and derived geospatial data.
The latest version of this standard is provided as a MSWord document on this CD-ROM.
A geospatial dataset file name should:
be less than 30 characters long
consist of lower case a-z and numerals 0-9
first character always a-z

37. Data Storage and Backup
Shared data in a service center must be on the f: drive.
Personal data can be stored on the c: drive or h: drive.
c: drive is not routinely backed up.
h: drive should contain important working files that can be routinely backed up.
Local Geodata Administrators are responsible for ensuring backups are routinely being made of specific directories.
Large, easily replaced datasets should not be routinely backed up because they can be obtained again.
Files and directories that change regularly should be routinely backed up.

38. GDB Design A critical step UML modeling for ArcGIS Class diagrams
IBM Rational Rose
MS Visio
Class diagrams
Unified modeling language

39. Managing Your GDB ArcCatalog is your main tool to manage the schema
Construction of component parts
Organization of those parts
Properties for the parts
Many capabilities are available
Some are not on the default GUI
ArcCatalog is your main tool for managing your Geodatabase. Almost all capabilities you will need (unless it is CASE tools) are available in ArcCatalog either through choosing the correct context sensitive menu or through choosing the correct tool.
Bear in mind there are advanced capabilities present in ArcCatalog, but they are not installed on the default user interface. To access these capabilities, you will need to customize your tool set. See the topic Customizing ArcMap and ArcCatalog in the Help tool.

40. Reading Schemas
Most data access technologies provide a way for you to query the schema of a database, and obtain information about the tables, stored procedures, data types, users, and other content of a database.
Logical
Structural

41. Creating a GDB Personal Multi-user Use ArcCatalog
Must be done at the system level
To create a Personal Geodatabase, you simply have to right-click while pointing your cursor at a directory. This will bring up a context-sensitive menu where you would choose New > Personal Geodatabase. You will then have the opportunity to rename the new Personal Geodatabase.
Creating a multi-user Geodatabase is beyond the scope of this class and must be performed by your system administrator. A

42. Creating a new personal geodatabase
Open ArcCatalog
Choose a folder location
Right click: Choose New < Personal Geodatabase

43. Right click your geodatabase Choose: New < Feature Dataset
Creating Feature Datasets
Right click your geodatabase
Choose: New < Feature Dataset

44. Creating an empty feature class
Two locations available: stand-alone and within a feature dataset
Again, right-click on your feature dataset where you wish to place a feature class. Perform these activities:
Choose New > Feature class
Click on Shape
Set Geometry Type
Set your Spatial Reference
Add and define additional attributes.
The resulting feature class will have all the properties for storing your geographic data, but will contain no data.
Note: be certain to define the shape geometry type: Line, Multipoint, Point, or Polygon.
You can add other attributes to the feature class by clicking on a blank field in the Field Name list, defining a name and the fields properties. A

45. Creating a feature dataset
By right-clicking on your Geodatabase (either Personal or Multi-User), you can choose New > Feature Dataset.
Simply fill out the information panels with the appropriate information. Be sure to specify your coordinate domains correctly, since this will control all feature class data placed within the Feature Dataset. A

46. Right click your geodatabase Choose: New < Feature Dataset
Creating Feature Datasets
Right click your geodatabase
Choose: New < Feature Dataset

47. Feature Datasets: Setting the spatial reference
Set the Projection
Set the Domain
Precision
Extent :
Search on Spatial Domain

48. Import existing data
Navigate to the feature dataset or geodatabase icon in ArcCatalog
Right Click
Choose Import
Use this to import any existing format!

49. Subtypes & Domains Subtype: Domain:
Distinguish features within a single layer
Maintain different domains within the same field
Need ArcEditor or ArcInfo
Domain:
Identify & constrain attribute values
Can utilize in ArcView

50. Subtypes & Domains Parcels
Example
Subtype: Boundary Line
Domains:
ROW Type

51. Subtypes Must be long or short integer fields
Created in ArcEditor or ArcInfo
Increases the efficiency of the editing process
Use when
Standardizing a legend
distinguishing different default values/domains within the same field

52. Creating Subtypes In ArcCatalog Double click on a feature class
Select the Subtype tab

53. Creating Domains Created in ArcCatalog
Double Click on the Personal Geodatabase Icon
Choose the Domains tab

54. Creating Domains—Assigning to Feature Classes
In ArcCatalog
Double click a feature class
Choose the Fields tab
Highlight a field
Click Domain under the Field properties section

55. Creating Domains—Assigning default values
Set in the Field Properties section
Use default values for common entries

56. Using Domains during the Editing Process

57. Geodatabase Topology Putting the power into your hands
Topology Rules
Preset rules to define topological relationships to ensure connectivity, adjacency and coincidence
Can be changed at any time
Topology Tools
Maintain spatial relationships
Toolbar and Tasks
Pro-West & Associates

58. Creating Topology Rules Cluster Tolerance Ranks
Land use boundaries overlap parcel boundaries
Manholes overlap sanitary line endpoints
Cluster Tolerance
Min distance where vertices within tolerance are snapped
Ranks
Control what features move during validating
Surveyed points will not move (snap) during the validation process
Pro-West & Associates

59. Validating Topology Validate edited features using set topology rules
Evaluate rules/tolerance and generates error notifications
Snaps vertices using set cluster tolerance and ranks
Pro-West & Associates

60. Create a New Topology Created in ArcCatalog
Created within a Feature Dataset
Topology Wizard
Allows user to set Rules, Ranks, Tolerance, and perform initial Validation
Pro-West & Associates

61. When added to ArcMap, will show errors from the validation process
Final Topology
When added to ArcMap, will show errors from the validation process

62. Managing Topologies
Right click on the Topology in ArcCatalog

63. Topology Tools Maintenance
Standard toolbar in ArcView-ArcInfo
Used in an editing environment in ArcMap
Use in conjunction with Topology Tasks in Editor Toolbar
Pro-West & Associates

64. Editor Toolbar Maintenance
Topology Tasks:
Modify, Auto Complete Polygon and Reshape
Allows user to use basic editing tools to alter vertices, replace lines, add adjacent polygons or alter existing polygons
Use in conjunction with the Topology Edit Tool on the Topology Toolbar
Remember:
Set snapping and snapping tolerance

65. Flexible Editing Topology edit tool Show shared features tool
Allows for editing shared boundaries
Builds a temporary topology cache within a given extent
Faster performance
Must use each time your extent changes
Show shared features tool
Move a boundary without effecting shared boundaries (temporary)
Parcels & land use
Parcels and easements
Pro-West & Associates

66. Validate & Fix Validate after editing is complete
Errors are highlighted
Click the Fix Error button
Select a feature and right click
Fix
Mark as an Exception
Do Nothing

67. Process in Review Plan for success Import data Set Subtypes & Domains
Create Topology
Start editing!
Pro-West & Associates

68. Tips Projecting data PGDB is 2 GB max
Must create a new feature class
PGDB is 2 GB max
Read-only on a PGDB will restrict some analyses, such as Select by Location
Use compact to clean up temporary files
All table names need to be unique
There are a number of tips you may find helpful as you work with a Geodatabase:
If you wish to project your feature class data into another coordinate system, you must create a new feature class. You should not attempt to change the coordinate system properties. Right-click on your feature class and choose Export > Geodatabase to Geodatabase.
If you have more than one Geodatabase (either type), you can drag and drop feature classes or feature datasets from one to another.
A Personal Geodatabase has a 2 Gigabyte maximum. Also, no rasters, CAD data or custom objects can be stored in Personal GeoDatabases.
If you place a read-only property on a Personal Geodatabase (since it is really a single file on your disk), you will be restricted on some activities such as Select by Location. This action requires temporary tables to be written to the Geodatabase.
Lots of temporary tables get written to a Geodatabase when certain activities are performed (such as Select by Location). To clean these tables out, use Compact.
All table names must be unique in a Geodatabase. This includes all feature classes inside or outside of a feature dataset.

69. Ex 2 Create a Personal GDB Create an empty Feature Class
Create a Feature Dataset
Create a Feature Class within the Feature Dataset