MAX_DUMP_FILE_SIZE

When choosing to use to parameter, be sure to use suffix (M or K). 

If you set max_dump_file_size=10000. 

This represents 10000 x block_size of ur server, e.g block_size for solaris=512bytes. HPUX=1024bytes, Windows/nt=512bytes.

If want to use value as 10M then use in below format: 

ALTER SYSTEM SET MAX_DUMP_FILE_SIZE='10M' scope=both;

Default value to this Parameter is unlimited.