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Oracle Tips by Robert Freeman

Using ORADEBUG To Set A Trace Event

ORADEBUG is the method I normally use to enable 10046 tracing of another session. It seems to be the most straightforward to me. Before we can use ORADEBUG, we need some information on the session we want to trace. In the query that we did earlier to identify the session we wanted to trace, did you notice that we also returned the SPID and PID columns? We did this to allow us to use ORADEBUG to connect to the session and direct it to start tracing, as you will see shortly.
To use ORADEBUG, we first need to start SQL*Plus and connect to the database as SYS using the SYSDBA login. You must have SYSDBA privileges to run ORADEBUG.
Next, we need to connect to the session by setting the ORADEBUG session to the OS Process id (PID) or to the Oracle ID (SPID) of the session we want to trace. For example, if we want to trace session SID 144, which is serial number 36 we would note that the SPID of that session is 1864, and the PID of that session is 21.
Now that we know this information, we are ready to use ORADEBUG. Here is an example using the SPID of the session to start tracing:
SQL> oradebug setospid 1864;
We could also use the PID to connect to the session as seen in this example:
SQL> oradebug setpid 21;
You can then instruct the session to begin tracing with this oradebug statement:
SQL> oradebug event 10046 trace name context forever, level 12
To disable tracing use this statement:
SQL> oradebug event 10046 trace name context off
Using DBMS_SYSTEM.SET_EV To Set A Trace Event
The dbms_system.set_ev procedure can be used to set events too. The procedure has the following syntax:
Dbms_system.set_ev (
si binary_integer, -- SID
se binary_integer, -- Serial#
ev binary_integer, -- Event code or number to set.
le binary_integer, -- Usually level to trace
cm binary_integer -- When to trigger (NULL = context
To enable 10046 level 12 tracing for SID 22 with a serial# of 99 we would execute the set_ev procedure as shown here:
Exec dbms_system.set_ev(22,99,10046,12,??);
To disable 10046 tracing enter the following:
Exec dbms_system.set_ev(12,22,10046,0,??);

Locating the Oracle Trace File

The location of the trace file that will get created is pointed to by the user_dump_dest parameter. ORADEBUG will also provide the location and name of the trace file:
SQL> oradebug tracefile_name
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