Group member: kainat ilyas #3 saman saleem #9 uos fsd women campus

presentation : Database

administration & management Topic : Trace File

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.

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

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.

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.

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.

SMON

• SMON stands for System Monitor.• SMON is an Oracle background process

created when you start a database instance

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.

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.

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.

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.

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.