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Oracle9i Supplied PL/SQL Packages and Types Reference
Release 2 (9.2)

Part Number A96612-01
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46
DBMS_PROFILER

Oracle8i provides a Profiler API to profile existing PL/SQL applications and to identify performance bottlenecks. You can use the collected profiler (performance) data for performance improvement or for determining code coverage for PL/SQL applications. Application developers can use code coverage data to focus their incremental testing efforts.

The profiler API is implemented as a PL/SQL package, DBMS_PROFILER, that provides services for collecting and persistently storing PL/SQL profiler data.


Note:

DBMS_PROFILER treats any program unit that is compiled in NATIVE mode as if you do not have CREATE privilege, that is, you will not get any output.


This chapter discusses the following topics:

Using DBMS_PROFILER

Improving application performance is an iterative process. Each iteration involves the following steps:

  1. Running the application with one or more benchmark tests with profiler data collection enabled.
  2. Analyzing the profiler data and identifying performance problems.
  3. Fixing the problems.

The PL/SQL profiler supports this process using the concept of a "run". A run involves running the application through benchmark tests with profiler data collection enabled. You can control the beginning and the ending of a run by calling the START_PROFILER and STOP_PROFILER functions.

A typical run involves:

As the application executes, profiler data is collected in memory data structures that last for the duration of the run. You can call the FLUSH_DATA function at intermediate points during the run to get incremental data and to free memory for allocated profiler data structures.

Flushing the collected data involves storing collected data in database tables. The tables should already exist in the profiler user's schema. The PROFTAB.SQL script creates the tables and other data structures required for persistently storing the profiler data.

Note that running PROFTAB.SQL drops the current tables. The PROFTAB.SQL script is in the RDBMS/ADMIN directory. Some PL/SQL operations, such as the first execution of a PL/SQL unit, may involve I/O to catalog tables to load the byte code for the PL/SQL unit being executed. Also, it may take some time executing package initialization code the first time a package procedure or function is called.

To avoid timing this overhead, "warm up" the database before collecting profile data. To do this, run the application once without gathering profiler data.

System-Wide Profiling

You can allow profiling across all users of a system, for example, to profile all users of a package, independent of who is using it. In such cases, the SYSADMIN should use a modified PROFLOAD.SQL script which:

Requirements

DBMS_PROFILER must be installed as SYS.

Use the PROFLOAD.SQL script to load the PL/SQL Profiler packages.

Collected Data

With the Probe Profiler API, you can generate profiling information for all named library units that are executed in a session. The profiler gathers information at the PL/SQL virtual machine level. This information includes the total number of times each line has been executed, the total amount of time that has been spent executing that line, and the minimum and maximum times that have been spent on a particular execution of that line.


Note:

It is possible to infer the code coverage figures for PL/SQL units for which data has been collected.


The profiling information is stored in database tables. This enables querying on the data: you can build customizable reports (summary reports, hottest lines, code coverage data, and so on. And you can analyze the data.

PROFTAB.SQL

The PROFTAB.SQL script creates tables with the columns, datatypes, and definitions as shown in Table 46-1, Table 46-2, and Table 46-3.

Table 46-1 Columns in Table PLSQL_PROFILER_RUNS
Column Datatype Definition

runid

number primary key

Unique run identifier from plsql_profiler_runnumber

related_run

number

Runid of related run (for client/server correlation)

run_owner

varchar2(32),

User who started run

run_date

date

Start time of run

run_comment

varchar2(2047)

User provided comment for this run

run_total_time

number

Elapsed time for this run in nanoseconds

run_system_info

varchar2(2047)

Currently unused

run_comment1

varchar2(2047)

Additional comment

spare1

varchar2(256)

Unused

Table 46-2 Columns in Table PLSQL_PROFILER_UNITS
Column Datatype Definition

runid

number

Primary key, references plsql_profiler_runs,

unit_number

number

Primary key, internally generated library unit #

unit_type

varchar2(32)

Library unit type

unit_owner

varchar2(32)

Library unit owner name

unit_name

varchar2(32)

Library unit name timestamp on library unit

unit_timestamp

date

In the future will be used to detect changes to unit between runs

total_time

number

Total time spent in this unit in nanoseconds. The profiler does not set this field, but it is provided for the convenience of analysis tools.

spare1

number

Unused

spare2

number

Unused

Table 46-3 Columns in Table PLSQL_PROFILER_DATA
Column Datatype Definition

runid

number

Primary key, unique (generated) run identifier

unit_number

number

Primary key, internally generated library unit number

line#

number

Primary key, not null, line number in unit

total_occur

number

Number of times line was executed

total_time

number

Total time spent executing line in nanoseconds

min_time

number

Minimum execution time for this line in nanoseconds

max_time

number

Maximum execution time for this line in nanoseconds

spare1

number

Unused

spare2

number

Unused

spare3

number

Unused

spare4

number

Unused

With Oracle8, a sample textual report writer(profrep.sql) is provided with the PL/SQL demo scripts.

Security

The profiler only gathers data for units for which a user has CREATE privilege; you cannot use the package to profile units for which EXECUTE ONLY access has been granted. In general, if a user can debug a unit, the same user can profile it. However, a unit can be profiled whether or not it has been compiled DEBUG. Oracle advises that modules that are being profiled should be compiled DEBUG, since this provides additional information about the unit in the database

Two Methods of Exception Generation

Each routine in this package has two versions that allow you to determine how errors are reported.

In each case, the parameters of the function and procedure are identical. Only the method by which errors are reported differs. If there is an error, there is a correspondence between the error codes that the functions return, and the exceptions that the procedures raise.

To avoid redundancy, the following section only provides details about the functional form.

Exceptions

Table 46-4
Exception Description

version_mismatch

Corresponds to error_version.

profiler_error

Corresponds to either "error_param" or "error_io".

DBMS_PROFILER Exceptions

Error Codes

A 0 return value from any function denotes successful completion; a nonzero return value denotes an error condition. The possible errors are as follows:


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