The trace log is used for incident, error and event reporting. Most of the errors that happen in the database are captured on the trace files. Oracle Database administrators also can turn on trace for specific sessions. The trace file is not well formatted, but you will be able to search the errors (all ORA-xxx errors).
The table below provides the default location for the log file and the query you can run in case location has changed.
|Log format||Oracle version||Tags||Default file location|
|Plain text||10g/11g/12c (Linux and Windows)|
show parameter USER_DUMP_DEST;