First, ENDJRN on all objects that are being journaled to that particular Journal.
You can do that by doing WRKJRNA &LIB/&JRN
F19 will show what is being journaled.
After you have ending journalling. Use F15 from the WRKJRNA to get a list of receivers. Take option 4 to delete them.
Now do DLTJRN &LIB/&JRN