For example, the trace files for PMON and SMON contain
an entry when an error occurs or when SMON needs to perform instance recovery; the trace
files for QMON contain informational messages when it spawns a new process.
Trace files are also created for individual user sessions or connections to the database. These
trace files are located in the directory specified by the initialization parameter USER_DUMP_
DEST. Trace files for user processes are created in two situations: The first is when some type of
error occurs in a user session because of a privilege problem, running out of space, and so forth.
In the second situation, a trace file can be created explicitly with the command alter session set
sql_trace=true. Trace information is generated for each SQL statement that the user executes,
which can be helpful when tuning a user??™s SQL statement.
The alert log file can be deleted or renamed at any time; it is re-created the next time an alert
log message is generated. The DBA will often set up a daily batch job (either through an operating
system mechanism or using Oracle Enterprise Manager??™s scheduler) to rename and archive the
alert log on a daily basis.
Backup Files
Backup files can originate from a number of sources, such as operating system copy commands
or Oracle Recovery Manager (RMAN). If the DBA performs a ???cold??? backup (see the section titled
???Backup/Recovery Overview??? for more details on backup types), the backup files are simply operating
system copies of the datafiles, redo log files, control files, archived redo log files, and so forth.
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