Someone beat me to it in this good post: Oracle Tip: Counting ROWS for all tables in a Schema . So here a reminder for me where to find it.
SELECT TABLE_NAME , to_number(extractvalue(xmltype( dbms_xmlgen.getxml('select count(*) c from '||TABLE_NAME)) ,'/ROWSET/ROW/C')) COUNT FROM user_tables;
That said, I don’t like the use of DBMS_XMLGEN (performance reasons/compatibility), so also for future reference, I also still have to come up with a better one. The use of extractvalue has at least the advantage that this one should be backwards compatible to 188.8.131.52.