I believe your mkt_outbound_staging might have a lock, its an internal table we use to stage rows for the DB or file template treatments, this is the staging table that holds this information prior to it being dispatched to the target table or file.
A batch job might got failed and the table would have got locked. You can unlock the table as below
1)Login to database(oracle) as sys/sysdba
2)Run the below query to obtain the lock information:
select a.sid, a.serial# from v$session a, v$locked_object b, dba_objects c where
b.object_id = c.object_id and a.sid = b.session_id and
3) Run the below query to kill the session and free the lock of the table:
alter system kill session 'sid,serial';
sid and serial are the input data which obtained from the first query.
Its difficult to find what would have caused this locking issue on the table by reviewing the above snippet. We will have to review the PegaRULES and Alert logs and need to review the appropriate rule or code (activity or any other rule involved) if that helps to identify the root cause.