Question: Is it one alert log per instance
or one per RAC database? I want to monitor by RAC alerts and I
need to know if Oracle has multiple alerts logs in RAC databases.
Are alert logs in the diagnostic_dest instance specific or
database specific? If they are instance specific, how can you
consolidate the alert log messages?
each instance in a RAC cluster has it's own alert log. The 11g
RAC Administrator's Guide under Appendix B Troubleshooting notes:
Using Instance-Specific Alert Files in Oracle RAC
Each instance in an Oracle RAC database has one alert file. The
alert file for each instance, alert.SID.log, contains important
information about error messages and exceptions that occur during
database operations. Information is appended to the alert file each
time you start the instance. All process threads can write to the
alert file for the instance.
The alert_SID.log file is in the
directory specified by the DIAGNOSTIC_DEST parameter in the
initdb_name.ora initialization parameter file.
For monitoring you alert logs, I use scripts to scan each alert
log in the RAC cluster for important messages and e-mail them to a
If you don't want to write your own custom scripts, see my
Oracle script download.
In 11g and beyond, you can directly query the alert log
with SQL, using
the alert log - You can define the alert log file as an
external table and detect important messages with SQL and e-mail
them to a central repository.
Scripts - You
Oracle shell scripts OS shell scripts to detect alert log
- The Ion tool has complete mechanisms for setting custom alert
PL/SQL - You
can write a SQL*Plus procedure using utl_file to read
the alert log.
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