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Don Burleson Blog 







Script to monitor the alert log

Oracle Database Tips by Donald BurlesonJuly 19,  2015

  I want to automate the monitoring of my Oracle alert log, and I want to write a program to monitor the alert log for messages.  What is the best way to monitor the alert log, externally with a shell script or by defining my alert log as an external table and using SQL?  Also, what alert log messages should I look for?

Answer:  It's important to monitor the Oracle alert log and send alerts when serious errors are logged into the alert log.  There are many approaches to detecting alert log messages and sending e-mail alerts:

  • SQL against the alert log - You can define the alert log file as an external table and detect messages with SQL.
  • Scripts - Write your own OS shell scripts to detect alert log messages.
  • PL/SQL - You can write a SQL*Plus procedure using utl_file to read the alert log.

A comprehensive alert log monitor is not trivial, and it can can take hundreds of hours to write and de-bug and maintain.  Many companies find it more cost effective and reliable to choose to use a remote DBA service that provides sophisticated alert log monitor software.

The key to monitoring the alert log for critical messages is to use regular expressions which are available either in UNIX/Linux shell scripts or with SQL regular expressions.  The script that I use on my remote DBA clients is very sophisticated and took hundreds of hours to develop, but simple alert log monitor scripts can be developed using the standard UNIX and Linux utilities.  An alert log monitor script may have these features:

1 - Records of all startups and shutdowns - Startup is in v$instance.startup_time, but shutdown data is problematic as it is only written to the alert log.  During a normal shutdown, Oracle writes message to the alert log, but under an emergency abort (i.e. un-plug the server), nothing appears in the logs, nor within Oracle. Oracle stops abruptly, and there is no way to see it, except periodic polling for a PMON or SMON process.

2 - Finds important unexpected events - Most people write an alert log monitor with ?exceptions?, designing a ?clean list? of alert log messages to ignore, and sending e-mail alerts for new, unexpected messages.  A complete Oracle monitoring package may alert for hundreds of metrics.

3 - Seeks important error messages - Using a utility like grep, you can easily find ORA-00600 errors, but it's a bit trickier to find "unexpected" messages.  While OEM has primitive alert log monitoring, real shops need scripts that are more sophisticated.



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