The fundamental cause of backup and restore problems is that the system has only been tested on small courses. It should be tested on a course designed to be larger in most aspects than courses that we expect to encounter at the OU and other institutions.

There should be a test process or script for testing large course backup/restore. (This should probably be separate from normal unit tests because it will take too long to run. It might involve an automated script that creates the stupidly big course, and then a manual test script to run through doing backup and restore.)

Specifically, this course should have the following features (there might be others but these are the factors we identified as critical):

• At least 5,000 activities spread across at least 1,000 sections.
• At least 50,000 enrolled users.
• Includes a single resource (File) containing at least 10,000 different files totalling at least 1GB.
• Includes a forum containing at least 1,000 discussions and 10,000 posts.
• In total across other activities, includes different files totalling at least 15GB.

A course of this size may well not backup/restore successfully with default Moodle settings; in order to make a course of this size successfully back up and restore, it will be necessary to do some or all of the following:

• Run on a 64-bit PHP platform.
• Increase the ‘extra memory limit’ to a large value by using a configuration option visible in admin settings.
• Set up paths to external zip and unzip utilities.
• Require certain minimum component versions.

You may need to install this admin tool as part of testing another issue. If you are using a version which already includes the fixes for MDL-41045 and MDL-41004, you should be able to just merge this branch into your code and then visit the Notifications page. It should now be available under the Developer menu.