The document discusses trace files in Oracle databases. Trace files are created by Oracle background processes like DBWR, LGWR, PMON and SMON to diagnose and resolve operating problems. When an error occurs, process information is written to its trace file. By default only the Oracle OS user can read trace files, but this setting can be changed. The name, location, and maximum size of trace files can also be configured.

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2. presentation :
Database
administration & management
Topic :
Trace File

3. Definition of Trace File
• Trace File are trace (or dump) file that Oracle
Database creates to help you diagnose and
resolve operating problems. Each server and
background process writes to a trace file.
When a process detects an internal error, it
writes information about the error to its trace
file.

4. Trace files in Oracle
• When one of the Oracle background processes
(such as dbwr, lgwr,pmon, smon and so on )
encounter an exception, they will write a trace
file.
• These trace files are also recorded in
the alert.log.
• Trace files are also created for diagnostic
dump events.
• An ORA-00600 error also produces a trace file

5. DBWR
• DBWR stands for database write.
• DBWR (DataBase WRiter) is an Oracle
background process created when you start a
database instance. The DBWR writes data
from the SGA to the Oracle database files.
When the SGA data buffer cache fills
the DBWR process selects buffers using an
LRU algorithm and writes them to disk.

6. LGWR
• LGWR stands for Log Writer.
• LGWR is an Oracle background process
created when you start a database instance.
The LGWR writes the redo log buffers to the
on-line redo log files.

7. PMON
• The process monitor database process.
• This process is in charge to perform process
recovery when a user process fails (also when
killed). It then cleans up the cache and frees
resources that the process used.

8. SMON
• SMON stands for System Monitor.
• SMON is an Oracle background process
created when you start a database instance

9. Public readability of trace files
• By default, trace files are only readable by
the Oracle OS user (on Unix, )
• This setting can be altered
with trace_files_public.

10. Name and location of the trace file
• The name of the trace file can be changed (to
make it easier to find it) with
• alter session set tracefile_identifier =
'some_id';
• Trace files are saved in user Dump-Dest.

11. Conti…
• user dump dest Is a specifies the path name
for a directory where the server will write
debugging trace file on behalf on a user
process.

12. Maximum size for a trace file
• The maximum size for trace files can be
specified with max_dump_file_size.
• MAX_DUMP_FILE_SIZE specifies the
maximum size of trace files (excluding the
alert file). Change this limit if you are
concerned that trace files may use too much
space.
• A numerical value
for MAX_DUMP_FILE_SIZE specifies the
maximum size in operating system blocks.

13. Conti…
• A number followed by a K or M suffix specifies
the file size in kilobytes or megabytes.
• 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.