Question:
What are the differences between the personal geodatabase in Microsoft Access and the file-based personal geodatabase for ArcGIS? When should I use one or the other? Do I need to convert all my existing .mdb GDBs to file based GDBs?
Answer:
There are several important changes to geodatabases at the release of ArcGIS 9.2. The following paragraphs outline some of these changes by focusing on the differences between the new file based geodatabase and existing personal geodatabase format. The Help Desk recommends that you evaluate the advantages and disadvantage of each for your particular projects.

Personal geodatabase (.mdb)
The personal geodatabase (PGDB) is contained within a Microsoft Access database file (.mdb) and is available at all ArcGIS licenses. The PGDB is appropriate for individual users and very small work groups. The reasons being that the PGDB is limited to 2GB of storage and performance can degrade with multiple readers when file size exceeds 250 MB.

One advantage of the PGDB is that database tables can be opened in Access for attribute only editing, making Access a useful attribute manager. PGDBs created in pervious versions of ArcGIS can be read and edited in v. 9.2 without having to upgrade the geodatabase (see ticket 1526). Older PGDBs must be upgraded if you intend on using new geodatabase functionality available only at 9.2 (see http://webhelp.esri.com/arcgisdeskto..._ArcGIS_92.pdf. Finally, ESRI will continue to support the PGDB.

File based geodatabase
The file based geodatabase (FGDB) is new at version 9.2 and is now the recommended native format for ArcGIS by ESRI. It makes use of binary files to store geographic datasets that exist within a folder on a disk drive. As such, an entire FGDB is represented as a file folder and is not tied to a relational database management system. The storage capacity for the FGBD is much greater than the PGDB - up to 1 terabyte (TB) per dataset.

The FGDB is appropriate for small workgroups and multiple data editors, so long as each editor is working on separate feature datasets, standalone feature classes or tables within the geodatabase. Otherwise it is recommended that there be one data editor per FGDB.

Performance for the FGDB is very fast as it uses 1/3 of the feature storage capacity required of a PGDB or shapefile. The benefit is that individual feature classes can scale up to 500 GB and still demonstrate fast performance. However, concurrent use of large datasets by a large number of users will produce degradations in performance.

The FGDB is supported on both Windows and Linux operating systems and is available to all licenses of ArcGIS.