Try doing a rebuild key files.

that's not an option in premium.

That would be a problem. I'm no SQL expert.

Do the records have some sort of deleted marker on them?

I hunted around and found a number of articles talking about reclaiming space in SQL databases (not specificially Sage 100).  They seem to suggest that the space from deleted records are not automatically reclaimed but that new records added will automatically overwrite the deleted records.

Apparently there are some commands that will shrink the actual database but they take a very long time to process.  Consensus seems to be that it isn't worth the time. 

I can handle the SQL side of things, that's not an issue for me. Shrinking a DB isn't the same as purging records.  But you are correct, the end goal is to purge records that are no longer needed & then shrink the DB to lower overall disk consumption.

Where I'm a little stuck is having Sage purge the proper records with their utilities.  I don't want to go down the rabbit hole of looking at every table and looking for records to delete. I'm just noticing that after using the purge tools for those modules, that there are at least those two SO tables that still have records going was past the date I set as the purge date.

Sorry.  Didn't pay attention to the specific files in question.

SO_LastPurchaseHistory

I believe you can purge that by going to Customer Last Purchase Maintenance in SO | Setup and clicking on the Rebuild button.  You might want to back up first.

The other file,  I don't know.

It looks like that took care of the last purchase history (had to use the clear option, not rebuild).  But the SO_ARInvoiceHistoryLink is still the same. Odd that you have to purge/clear in so many different places.

Are you running Period End for all modules?  Are the "Years To Retain" settings in module options configured properly?  Normally purges happen automatically during Period End processing for the last period of a fiscal year.

they were not set appropriately, but I've changed them prior to attempting to purge data.

For all Framework modules you can "rewind" the fiscal period (in module options) and re-run period end for the last period in the previous year.  (Don't do this for non-Framework modules).

I assume you did a clear followed by a rebuild?  basically the rebuild will reconstruct everything from the remaining history after the purge.