SPARQL queries should not report success, if all the data has not actually loaded.
When loading large datasets, it is common to get an error of the form --
[Virtuoso Server]SR325: Transaction aborted because it's log after image size went above the limit
This results from the transaction log filling up while attempting to load a large dataset.
Such errors should be revealed by a review of the virtuoso.log.
For best results, we recommend loading large data sets with the RDF Bulk Load scripts.
You may also choose to get around this error by splitting large files into small chunks and loading each separately, or using these two functions (which are part of what the Bulk Load scripts use):