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Oracle® Database PL/SQL Packages and Types Reference
11g Release 1 (11.1)

B28419-03
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136 DBMS_TRACE

The DBMS_TRACE package contains the interface to trace PL/SQL functions, procedures, and exceptions.

This chapter contains the following topics:


Using DBMS_TRACE


Overview

DBMS_TRACE provides subprograms to start and stop PL/SQL tracing in a session. Oracle collects the trace data as the program executes and writes it to database tables.

A typical session involves:


Security Model

This package must be created under SYS.


Constants

The DBMS_TRACE package uses the constants shown in Table 136-1, "DBMS_TRACE Constants":

Table 136-1 DBMS_TRACE Constants

Name Type Value Description

TRACE_MINOR_VERSION

INTEGER

0

 

TRACE_MAJOR_VERSION

INTEGER

1

 

TRACE_ALL_CALLS

INTEGER

1

Traces calls or returns

TRACE_ENABLED_CALLS

INTEGER

2

 

TRACE_ALL_EXCEPTIONS

INTEGER

4

Traces exceptions

TRACE_ENABLED_EXCEPTIONS

INTEGER

8

Traces exceptions and handlers

TRACE_LIMIT

INTEGER

16

Save only the last few records. This allows tracing up to a problem area, without filling the database up with masses of irrelevant information. If event 10940 is set, the limit is 1023*(the value of event 10940). This can be overridden by the use of "TRACE_LIMIT" flag.

TRACE_ALL_SQL

INTEGER

32

Traces SQL statements

TRACE_ENABLED_SQL

INTEGER

64

Traces SQL statements at PL/SQL level. This does not invoke SQL Trace

TRACE_ALL_LINES

INTEGER

128

Traces each line

TRACE_ENABLED_LINES

INTEGER

256

 

TRACE_PAUSE

INTEGER

4096

Pauses trancing

TRACE_RESUME

INTEGER

8192

Resume tracing

TRACE_STOP

INTEGER

16384

Stops tracing

NO_TRACE_ADMINISTRATIVE

INTEGER

32768

Prevents tracing of 'administrative events such as

  • PL/SQL Trace Tool started

  • Trace flags changed

  • PL/SQL Virtual Machine started

  • PL/SQL Virtual Machine stopped

NO_TRACE_HANDLED_EXCEPTIONS

INTEGER

65536

Prevents tracing of handled exceptions


Oracle recommends using the symbolic form for all these constants.


Restrictions

You cannot use PL/SQL tracing in a shared server environment.


Operational Notes

Controlling Data Volume

Profiling large applications may produce a large volume of data. You can control the volume of data collected by enabling specific program units for trace data collection.

You can enable a program unit by compiling it debug. This can be done in one of two ways:

ALTER SESSION SET plsql_debug=TRUE; 
CREATE OR REPLACE ... /* create the library units - debug information will be generated */ 

or:

/* recompile specific library unit with debug option */ 
alter [PROCEDURE | FUNCTION | PACKAGE BODY]  <libunit-name> compile debug; 

Note:

You cannot use the second method for anonymous blocks.

You can limit the amount of storage used in the database by retaining only the most recent 8,192 records (approximately) by including TRACE_LIMIT in the TRACE_LEVEL parameter of the SET_PLSQL_TRACE procedure.

Creating Database Tables to Collect DBMS_TRACE Output

You must create database tables into which the DBMS_TRACE package writes output. Otherwise, the data is not collected. To create these tables, run the script TRACETAB.SQL. The tables this script creates are owned by SYS.

Collecting Trace Data

The PL/SQL features you can trace are described in the script DBMSPBT.SQL. Some of the key tracing features are:

Additional features of DBMS_TRACE also allow pausing and resuming trace, and limiting the output.

Tracing Calls

Two levels of call tracing are available:

Enabling cannot be detected for remote procedure calls (RPCs); hence, RPCs are only traced with level 1.


Tracing Exceptions

Two levels of exception tracing are available:


Tracing SQL

Two levels of SQL tracing are available:


Tracing Lines

Two levels of line tracing are available:

When tracing lines, Oracle adds a record to the database each time the line number changes. This includes line number changes due to procedure calls and returns.

Note:

For all types of tracing, level 1 overrides level 2. For example, if both level 1 and level 2 are enabled, then level 1 takes precedence.

Collected Data

If tracing is requested only for enabled program units, and if the current program unit is not enabled, then no trace data is written.

When tracing calls, both the call and return are traced. The check for whether tracing is "enabled" passes if either the called routine or the calling routine is "enabled".

Call tracing will always output the program unit type, program unit name, and line number for both the caller and the callee. It will output the caller's stack depth. If the caller's unit is enabled, the calling procedure name will also be output. If the callee's unit is enabled, the called procedure name will be output

Exception tracing writes out the line number. Raising the exception shows information on whether the exception is user-defined or pre-defined. It also shows the exception number in the case of pre-defined exceptions. Both the place where the exceptions are raised and their handler is traced. The check for tracing being "enabled" is done independently for the place where the exception is raised and the place where the exception is handled.

All calls to DBMS_TRACE.SET_PLSQL_TRACE and DBMS_TRACE.CLEAR_PLSQL_TRACE place a special trace record in the database. Therefore, it is always possible to determine when trace settings were changed.

Trace Control

As well as determining which items are collected, you can pause and resume the trace process. No information is gathered between the time that tracing is paused and the time that it is resumed. The constants TRACE_PAUSE and TRACE_RESUME are used to accomplish this. Trace records are generated to indicate that the trace was paused/resumed.

It is also possible to retain only the last 8,192 trace events of a run by using the constant TRACE_LIMIT. This allows tracing to be turned on without filling up the database. When tracing stops, the last 8,192 records are saved. The limit is approximate, since it is not checked on every trace record. At least the requested number of trace records will be generated; up to 1,000 additional records may be generated. The 8,192 record limit can be changed. Setting event 10940 to level n changes the record limit to 1024 * n.


Summary of DBMS_TRACE Subprograms

Table 136-2 DBMS_TRACE Package Subprograms

Subprogram Description

CLEAR_PLSQL_TRACE Procedure

Stops trace data dumping in session

GET_PLSQL_TRACE_LEVEL Function

Gets the trace level

PLSQL_TRACE_VERSION Procedure

Gets the version number of the trace package

SET_PLSQL_TRACE Procedure

Starts tracing in the current session



CLEAR_PLSQL_TRACE Procedure

This procedure disables trace data collection.

Syntax

DBMS_TRACE.CLEAR_PLSQL_TRACE; 

GET_PLSQL_TRACE_LEVEL Function

This procedure returns the current trace level as a list of the enabled constants.

Syntax

DBMS_TRACE.GET_PLSQL_TRACE_LEVEL 
  RETURN BINARY_INTEGER; 

PLSQL_TRACE_VERSION Procedure

This procedure gets the version number of the trace package. It returns the major and minor version number of the DBMS_TRACE package.

Syntax

DBMS_TRACE.PLSQL_TRACE_VERSION ( 
   major OUT BINARY_INTEGER, 
   minor OUT BINARY_INTEGER); 

Parameters

Table 136-3 PLSQL_TRACE_VERSION Procedure Parameters

Parameter Description

major

Major version number of DBMS_TRACE.

minor

Minor version number of DBMS_TRACE.



SET_PLSQL_TRACE Procedure

This procedure enables PL/SQL trace data collection.

Syntax

DBMS_TRACE.SET_PLSQL_TRACE ( 
   trace_level INTEGER); 

Parameters

Table 136-4 SET_PLSQL_TRACE Procedure Parameters

Parameter Description

trace_level

You must supply one or more of the constants as listed in Table 136-1, "DBMS_TRACE Constants". By summing the constants, you can enable tracing of multiple PL/SQL language features simultaneously. The control constants "TRACE_PAUSE", "TRACE_RESUME" and "TRACE_STOP" should not be used in combination with other constants

Also see "Collecting Trace Data"  for more information.