With Database 12c, Oracle has provided a handy feature, Queryable Patch Inventory, which allows for a SQL and PL/SQL interface to the product patch inventory. Previously, this information was only accessible through the OS command: OPatch. Now, with the DBMS_QOPATCH package, you can monitor distributed Opatch repositories from a central location.
OPatch now supports inventory in XML format and inventory data is stored in database tables. So as data is stored in database tables, you can view installed database patches performing interactive queries using SQL*Plus. Oracle database 12c provides DBMS_QOPATCH package to manage this interface. It is installed by default during instance creation or by executing “dbmsqopi.sql” SQL script.