Identifying Locked Objects in Oracle Applications

At my site, we have a custom program to print invoices. That program prints invoice and updates printing_count, printing_last_printed columns of ra_customer_trx_all table. Sometime user were modifying the invoice using transaction workbench and they submit invoice print program without committing the changes in transaction workbench. So Invoice printing program would keep on waiting for lock on ra_customer_trx_all to be released. If that happened, user would call us to find what is happening and the following query was helpful to find out out who is locking the transaction table

SELECT obj.object_name , obj.object_type , blocked.client_identifier blocked_user , blocked.module , blocking.client_identifier blocking_user , blocking.module FROM gv$lock lck , dba_objects obj , gv$session blocking , gv$session blocked WHERE blocked.blocking_session = blocking.sid and lck.id1 = obj.object_id and blocked.sid = lck.sid