max_dump_file_size in 12c

MAX_DUMP_FILE_SIZE specifies the maximum size of trace files (excluding the alert log).

• A numeric value for MAX_DUMP_FILE_SIZE specifies the maximum size in operating system blocks.
• A numeric value followed by a K or M or G suffix specifies the file size in kilobytes, megabytes, or gigabytes.
• The special value string UNLIMITED means that there is no upper limit on trace file size. Thus, dump files can be as large as the operating system permits.

The trace file can be split into a maximum of 5 segments, and the size of each segment will typically be 1/5th of the trace file limit.