DELETE in openlink virtuoso

Hi to all,

I executed the following queries on a graph through ISQL

select count(?s)
from <example_graph>
	?s ?p ?o .
        ?s a example:Class1 .

Then i deleted all the entries of Class1 through this query

WITH <example_graph>
	?s a example:Class1 .

From SPARQL documentation I know that this operation is irreversible. Is it provided in Openlink Virtuoso a mechanism such that the data is stored somewhere until the graph is up? I ask this cause, after executing again an ETL process related to this Class1, the data are ingested in Virtuoso, but the ?s deleted previously just reappear like a kind of magic.

Thank you in advance.

What is the ETL process being performed, as if the triples have been deleted, then I can only assume the ETL process being performed is re inserting the triples previously deleted.

Can you provide step to recreate the problem ?