If you are having difficulties with MR Trace and Oracle 12, it may be due to changes in the way Oracle tells us where trace files are located. The parameter USER_DUMP_DEST has been deprecated, and may or may not point to the right file system directory.
If you have troubles, just execute the following PL/SQL as SYS user, and the directory objects that MR Trace needs will be corrected.
for v in (select g.inst_id, v.value from gv$instance g, v$diag_info v where v.name = 'Diag Trace')
execute immediate 'CREATE OR REPLACE DIRECTORY METHODR_UDUMP_' || v.inst_id || ' AS ''' || v.value || '''' ;
execute immediate 'GRANT READ ON DIRECTORY METHODR_UDUMP_' || v.inst_id || ' TO PUBLIC';
execute immediate 'CREATE OR REPLACE DIRECTORY METHODR_UDUMP_DEST AS ''' || v.value || '''';
execute immediate 'GRANT READ ON DIRECTORY METHODR_UDUMP_DEST TO PUBLIC';
If you wish to change the "PUBLIC" to a single role or schema, please feel free, but please do not alter the directory names. MR Trace needs those as is.
Yes, I do understand the code is not very elegant and executes the METHODR_UDUMP_DEST more than necessary in RAC environments with more than 1 node. Consider that refactoring an exercise for the reader