Making Sure Access Logs Are Tamed

It looks like there's a bug in Drupal 7 where, if you ever turn on and activate the Statistics module (enabling the logging of accesses to the database), and then decide to turn off the Statistics module, Drupal keeps on logging to the table that it creates (accesslog), and cron never clears anything out of that table, so it can just keep growing indefinitely.  On a busy site, this can result in multiple millions of entries in that table.

Here's what you can do to check for this condition:

1. If you know how to use something like phpMyAdmin to examine your database, look for an accesslog table (it may have a prefix on it, depending on how your copy of Drupal was set up).  If it exists, then your site has Statistics turned on, or did at some point in the past.  If the number of rows is huge, then you probably need to do the next step.
2. If you know you need to fix this problem, or if you don't know how to use phpMyAdmin, you can do the following:
   1. Go into your Drupal site and turn on the Statistics core module.  
   2. Next, go to Administration -> Configuration -> System -> Statistics and look at the settings there.  Disable Enable access log, set Discard access logs older than to '1 hour', and then save the configuration.  
   3. Finally, go to Administration -> Reports -> Status report, and initiate a manual cron run to clear the accesslog table.  Note that this may fail to complete if you have over a million entries in the table.  If so, then you'll need to use phpMyAdmin or something similar to clear out the table.
   4. Once you've gotten past step 2.3, go back to your Modules page and disable Statistics.

Of course, if you actually want to use the Statistics module, then make sure that Discard access logs older than is set to something other than 'never', so that the accesslog table doesn't grow indefinitely.