Donald K. Burleson Oracle Tips

Adding Custom Messages to the Oracle alert log

In Oracle, all major system messages are written to the Oracle alert log.  In order to create a single place for all Oracle system messages, the Oracle professional must develop a method for writing application messages into the alert log file.

By consolidating all Oracle messages (both system messages and application messages) database administration is greatly simplified because a central file exists for all Oracle-related alert messages.

The Oracle DBA can create a global PL/SQL stored procedure handle this interaction with the alert log file, and the global package can be called, passing the appropriate message to the procedure.  Here is an example of this type of call:

when others then

   dbms_custom.write_alert(:p_sysdate||‘ Application error’||:var1||’ encountered’);

This easy writing to the alert log is accomplished by using Oracle’s utl_file package.  The utl_file package allows Oracle SQL and PL/SQL to read and write directly from flat files on the server.

Writing custom messages to the Oracle alert log requires the following steps:

1. Locate the background dump directory (the location of the alert log).

2. Set the utl_file_dir initialization parameter.

3. Execute utl_file.fopen to open the file for write access.

4. Use dbms_output.put_line to write the custom message to the alert log.

5. Execute utl_file.fclose to close the file

Here is a code example for Oracle9i that illustrates the process:

-- ******************************************************

-- Gather the location of the alert log directory

-- ******************************************************

select

   name into :alert_loc

from

   v$parameter

where

   name = ‘background_dump_destination’;

-- ******************************************************

--  Set the utl_file_dir

--   (prior to Oracle9i, you must bounce the database)

-- ******************************************************

alter system set utl_file_dir = ‘:alert_log’);

-- ******************************************************

--  Open the alert log file for write access

-- ******************************************************

utl_file.fopen(':alert_loc',’alertprod.log’,'W');

-- ******************************************************

--  Write the custom message to the alert log file

-- ******************************************************

dbms_output.put_line('invalid_application_error');

-- ******************************************************

--  Close the alert log file

-- ******************************************************

utl_file.fclose(':alert_loc');

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