There are many cases where the Oracle DBA may
want to write custom messages directly into the standard Oracle
alert log file (located in $ORACLE_HOME/admin/$ORACLE_SID/bdump).
Why write to the alert log?
In Oracle11g and beyond, you can directly query the
alert log with SQL, using
By writing custom messages to the Oracle alert
log file you can supplement your default Oracle alerts with custom
If you don't want to write your own scripts to write to the
alert log, see my
Writing to the Oracle alert log is exactly the
same as writing to any flat file and we have these choices:
Alert log x$dbgalertext
- OS scripts and languages - You can use
UNIX/Linux utilities to write OS messages (e.g. RAM swapping
alerts) into the alert log. Of course, all procedural
languages (C++) can also write messages to the Oracle alert log.
- PL/SQL - You can use the standard utl_file
package or call the dbms_system.ksdwrt procedure to write messages
to the Oracle alert log file. See
Oracle utl_file Package and
Oracle alert log in stored procedure .
- SQL (read only) - You can define the alert
log as an external table and access the alert log messages with
SQL statements. See
Oracle Access your Alert Log via SQL with External Tables and
Extract alert log messages with SQL.
- dbms_output.put_line - This can be directed
to write to the alert log file.
- utl_file.put_line - This will also write to
the alert log.
- dbms_system.ksdwrt - This little-known
undocumented utility will write to the alert log.
Here are some example scripts of writing to the
Examples of writing to the alert log
dbms_output.put_line: This writes from Oracle to the alert log
not a utility per se, the ability to write
messages to the Oracle alert log is an extremely
This is being
mentioned in this chapter because it is an often
needed and useful, but not well documented
There are many cases where
the Oracle DBA may want to write custom messages
directly into the standard Oracle alert log file
located in $ORACLE_HOME/admin/$ORACLE_SID/bdump.
writing custom messages to the Oracle alert log
the default Oracle
alerts can be supplemented with custom messages.
The best method to write
to the alert log is to use
This very handy
utility will write a message to the alert log;
it takes two arguments, a number (1 or 2), and
indicates whether to write to alert or trace.
If set to 1, it
writes to a trace file.
If 2, it writes to
the alert log.
Because it uses the
dbms_system package, write a wrapper around the
call and grant privileges to the wrapper
procedure or function. Then an execute will not
have to be granted on the dbms_system package.
A possible function
to accomplish this purpose is below:
create or replace
function write_alert_log(log_or_trace in
number, text_message in varchar2) return
It is also possible to write to the alert log
using utl_file, but there are many privilege
issues that arise when using this method and
many more lines of programming.
The easy method is to use the
My notes on writing to the Oracle alert log