My quick test running OrderEntry 8.1E and the current service pack had the item history inquiry find transactions for a single specific item and customer (no ranges) in about a second, where the OEHLIN'R.dat data file was a shade under 500Mb and the programs and data are on a network drive (not local). The sort order for me was Item, Customer, Invoice date.

My ADS32.DLL is version 1.12.54.2989, which may be more current than what you have, but with current Adagio versions installed, the ADS is likely not too far behind.

I presume that your client's history is significantly larger than this, but I did not see any order of magnitude slowness when selecting a single item number for the inquiry on company data with a reasonable large history detail file.

As for your original question about 'what could have changed overnight', do they regularly do the single item/customer lookup? Just so the speed comparison is not based on the scenarios you found in your tests. Also, Miscrosoft released their round of Windows Updates yesterday, so it is entirely possible that one of these had an influence since this was a potential change yesterday. Anything else installed or changed at your client site yesterday, either Adagio related or not?