I have an Activity table which is getting all the table events of the system. Events like new orders, insertion/deletion on all the system tables will be inserted into this
You should try to use DBMS_PARALLEL_EXECUTE (since RDBMS 11).
https://blogs.oracle.com/warehousebuilder/entry/parallel_processing_in_plsql
https://oracle-base.com/articles/11g/dbms_parallel_execute_11gR2