Oracle has a feature called readonly transaction. Its main purpose is to ensure that for the lifetime of the transaction the data will not change.
Imagine the following senario: You read the accounts table, and the first account has a balance of X USD. As you go through the table another user commit his changes. If the transaction debits an already read account and credits another that is not yet read the report will never balance.
This is avoided by issuing the "set transaction read only" command before running the report. Maybe qlik is (correctly) doing the same in the background before sending the sql/plsql to oracle.
