What is auto trace used for? Is this a command or a function? Someone highlight me on this.
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What is auto trace used for? Is this a command or a function? Someone highlight me on this.
When auto trace is set to on it will cause each query that is getting executed to display the execution path along with the query. Auto trace is a command that can be set on or off as per the needs of the user.
it is a command which is used to display the execution path of the under lined query.
autotrace is used for to see the actual execution of sql.
it shows the all the path and how your query goes.
it mostly use for the tunning point of view.
Thanks and regard
Dhiraj Pande.
The autotrace utility is a very underutilized feature of SQL*Plus. It offers statement tracing and instant feedback on any successful SELECT, INSERT, UPDATE or DELETE statement. The utility requires a plan table (for the Explain Plan) under the current users schema. In addition, it requires the plustrace or DBA role for the user executing the trace. The source for the PLUSTRACE role can be found in
$ORACLE_HOME/sqlplus/admin/plustrce.sql.
Tracing is enabled via the set autotrace command in SQL*Plus:
SQL> set autotrace on
SQL> select ename from emp where empno = 1122;
no rows selected
Execution Plan
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=CHOOSE
1 0 TABLE ACCESS (BY INDEX ROWID) OF 'EMP'
2 1 INDEX (UNIQUE SCAN) OF 'PK_EMP' (UNIQUE)
Statistics
----------------------------------------------------------
83 recursive calls
0 db block gets
21 consistent gets
3 physical reads
0 redo size
221 bytes sent via SQL*Net to client
368 bytes received via SQL*Net from client
1 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
0 rows processed
autotrace provides instantaneous feedback including the returned rows, execution plan, and statistics. The user doesnt need to be concerned about trace file locations and formatting since the output is displayed instantly on the screen. This is very important data that can be used to tune the SQL statement.
autotrace supports the following options:
on Enables all options.
on explain Displays returned rows and the explain plan.
on statistics Displays returned rows and statistics.
trace explain Displays the execution plan for a select statement without actually executing it.
set autotrace trace explain
traceonly Displays execution plan and statistics without displaying the returned rows. This option should be used when a large result set is expected.
autotrace is so easy to use that it should be the first tracing utility used for most SQL performance tuning issues. tkprof can be used for more detailed analysis.