How to Prevent PHP notices logging to watchdog
dblog is one of the handy features of Drupal. It's a core module that monitors your system, capturing system events to database (or to *nix syslog with syslog module). This is useful for site administrators who want a quick overview of activities on their site. It also records the PHP warnings and notices. Notices are often trivial and they could be ignored from logging, IMO.
While it is essential to keep your Drupal site free from throwing any PHP notices, but in the current trend where most of the Drupal 7 modules are in beta / pre-beta stage it has been hard to ensure.
I figured out that adding the following code to settings.php prevents Drupal from logging PHP notices and gives room for other useful events.
ini_set('error_reporting', E_ALL ^ E_DEPRECATED ^ E_NOTICE);