The Top Nine Reasons to Use a File Geodatabase A scalable and speedy choice for single users or small groups By Colin Childs, Esri Education Services Whether you are working with large or small datasets, file geodatabases optimized for use in ArcGIS are ideal for storing and managing geospatial data. Whether you are working on a single-user project or a project involving a small group with one or several editors, you really should consider using a file geodatabase rather than a personal geodatabase or collection of shapefiles. File geodatabases offer structural, performance, and data management advantages over personal geodatabases and shapefiles. Structural 1. Improved versatility and usability 2. Optimized performance 3. Few size limitations 4. Easy data migration 5. Improved editing model 6. Storing rasters in the geodatabase 7. Customizable storage configuration 8. Allows updates to spatial indexes 9. Allows the use of data compression Performance Data Management 1 Improved versatility and usability 3 4 5 Few size limitations 6 Storing rasters in the geodatabase The file geodatabase is stored as a system folder that contains binary files that store and manage geospatial data. It is available at all ArcGIS license levels and functions in the same fashion on Windows and UNIX (Solaris and Linux) operating systems. This storage system is based on relational principles and provides a simple, formal data model for storing and working with information in tables. Open a file geodatabase folder in Windows Explorer, and it looks like any other folder. You can view the files it contains: geographic data, attribute data, index files, lock files, signature files, and other files. Each feature class or table in the geodatabase is stored in two or more files. Database size is limited only by available disk space. By default, individual tables and feature classes can be up to 1 TB. With the use of configuration keywords, this can be expanded to 256 TB. Easy data migration Because file geodatabases and personal geodatabases are both designed to be edited by a single user and do not support geodatabase versioning, data migration between them is easy. 2 Improved editing model Optimized performance The data structure of a file geodatabase is optimized for performance and storage. Although individual feature classes can be as large as 1 terabyte (TB) in size and contain hundreds of millions of features, they still provide fast performance. File geodatabases significantly outperform shapefiles for operations involving attributes and allow scaling of dataset size limits way beyond those of shapefiles. File geodatabases do not lock down the whole geodatabase if a user is editing a feature class. An edit model similar to that used for shapefiles is deployed. This model supports a single data editor and many data viewers concurrently. Stand-alone feature classes, tables, and feature dataset contents can be edited by different editors simultaneously without the entire geodatabase being locked. If a feature class in a feature dataset is being edited, all feature classes in that feature dataset are unavailable for editing, but features may still be viewed and selected in ArcMap. Raster storage in a file geodatabase shares functionality from both the ArcSDE geodatabase and the personal geodatabase. Managed raster data is stored in the same way as in an ArcSDE geodatabase, and unmanaged raster data is stored in the same way as in a personal geodatabase. Managed raster data is subdivided into small, manageable areas called tiles, stored as binary large objects (BLOBs) in the database. The tiling is automatic and invisible to end users. These tiles are indexed and pyramided for fast display performance. Pyramiding allows the geodatabase to fetch only data at the specified resolution or level required for display. Unmanaged rasters are maintained by users. Only the path to the location on the disk where the raster dataset is stored is maintained in the file geodatabase. 7 Customizable storage configuration When creating a dataset, apply optional configuration keywords to customize data storage. Keywords optimize storage for a particular type of data to improve storage efficiency and performance. 12 ArcUser Spring 2009 www.esri.com