At times we find it necessary to suspend a process at the OS level, in particular the RMAN backups. The backup adds I/O and can have an impact on performance specifically when file loads or other processes that make use of the UTL_FILE package within Oracle.
To suspend the process find the pid — where rman would be the key words to find the process.
ps -ef|grep rman
oracle 25685 4135
The first number is the parent process id.
kill -STOP 25685
To resume the process
kill -CONT 25685
Might also be a good idea to check the progress of RMAN. If it’s close to completion I would let it be.