VERIFIED SOLUTION i

Will the use of the Spectrum PGD files speed up the performance of Find My Nearest searches in Spectrum Spatial Analyst

The PGD index is a special kind of optional index that can be created on a TAB file and it's purpose is to make Find Nearest and Point in Polygon searches faster:
http://support.pb.com/help/spectrum/12.1/en/webhelp/ReleaseNotes/index.html#XChunk1546447102.html#performance
 
A TAB file that has a PGD index should perform quicker in Spectrum® Spatial 12.1 when Spectrum Spatial Analyst (SSA) makes Find Nearest searches.  
However, for most TAB files in SSA the difference is going to be minimal. SSA for example makes one nearest request at a time and the TAB files are usually small (or often the nearest searches are on point tables).
 
A PGD index gives a performance boost when running data flows that make many multiple requests and in cases when the TAB files are particularly complex (like flood zones (where there may be 100,000s nodes in a complex polygon), cell coverage polygon etc). If there's reason to believe that a suitably complex TAB file is being used then it would be worthwhile for the user to test running a Find Nearest both with and without an associated PGD file.

The PGD Builder utility can be downloaded from the Spectrum Spatial section of the Welcome Page, under PGD Builder on the Utilities tab. A link to the documentation for PGD Builder is also available on the Welcome Page next to the download link for the utility.
 
 
Environment Details
Products affected: Spectrum Spatial Analyst
UPDATED:  November 15, 2017