To test this: At present it is not possible to synchronise course categories from an external database in moodle. After applying this patch, create an external database. The following assumes that you're using postgres, and have a user 'moodle'.: – Creating our test dataset sudo su - postgres createdb -O moodle -EUTF8 externaldb cat <<EOF | psql externaldb CREATE TABLE categories ( id integer NOT NULL, title character varying(255) NOT NULL, description text, parent integer ); ALTER TABLE public.categories OWNER TO moodle; EOF Create some data in the categories cat <<EOF | php5 | psql externaldb <?php echo "INSERT INTO categories (id, title, description, parent) VALUES (1, 'Top Level', 'Description for Top Level', null);\n"; \$i = 2; while (\$i <= 6) { echo "INSERT INTO categories (id, title, description, parent) VALUES (\$i, 'Faculty \$i', 'Description for Faculty \$i', 1);\n"; \$j = 1; while (\$j <= 5) { echo "INSERT INTO categories (id, title, description, parent) VALUES ({\$i}00{\$j}, 'Department {\$j}', 'Description for Department {\$i}', {\$i});\n"; \$j++; } \$i++; } EOF – Iniial Configuration Now configure the enrolment/database module as follows: Site administration -> Plugins -> Enrolments -> Manage enrol plugins Enable "External database" Navigate to Settings page for External database Set database driver, host, user, password, and name as you've set them for your database Under "Creation of new Course Categories" Set "External course categories table" to: categories Set "Course Category id field" to: id Set "Course Category name field" to: title Leave the parent, and description fields blank for the moment as we'll use these to test updates, and re-parenting. Now run a cli sync: — Test Initial sync Open a shell, and switch to your web server user. Under debian I do: sudo su - www-data bash cd ~/git/moodle php enrol/database/cli/sync.php In Moodle, you should now have lots of top level categories. Open one of the categories in the category editor and verify that it has: the correct name; a category id number as appears in the database (e.g. Faculty 2 has idnumber 2; Faculty 2 -> Department 3 has idnumber 2003); and no description. — Test Setting a Category Parent Navigate back to the plugin's settings page and Set "Course Category parent field" to: parent Run the cli sync again In Moodle, the categories should now be re-parented. You should now have a top level category, with five sub-categories, each having five further sub categories — Test Setting a Category Description Navigate back to the plugin's settings page and Set "Course Category description field" to: description Set the "Format of Course Category description field" to "Plain text format" Run the cli sync again Open the same category again and verify that it now has the correct description and format. — Testing Deletion echo "DELETE FROM categories;" | psql externaldb Run the cli sync again All categories should be deleted with the exception of the "Top Level" category. It is not possible to delete this using the standard moodle category_delete_move All courses should have been re-parented to the "Top Level" category. — Testing a stupdily large dataset Please note that the Moodle interface doesn't actually work at all well with this many. This test merely proves that the category sync doesn't hog memory Ensure that you have the following set in your moodle config: define('MDL_PERF' , true); define('MDL_PERFDB' , true); define('MDL_PERFTOLOG' , true); define('MDL_PERFTOFOOT', true); I stress, moodle cannot handle this number of course categories. It cannot render the Edit Courses page with this many. This is a purely a test to demonstrate that this patch is really pretty memory efficient cat <<EOF | php5 | psql externaldb <?php echo "INSERT INTO categories (id, title, description, parent) VALUES (1, 'Top Level', 'Description for Top Level', null);\n"; \$i = 2; while (\$i <= 99) { echo "INSERT INTO categories (id, title, description, parent) VALUES (\$i, 'Faculty \$i', 'Description for Faculty \$i', 1);\n"; \$j = 1; while (\$j <= 99) { echo "INSERT INTO categories (id, title, description, parent) VALUES ({\$i}00{\$j}, 'Department {\$j}', 'Description for Department {\$i}', {\$i});\n"; \$j++; } \$i++; } EOF echo "SELECT COUNT FROM categories;" | psql externaldb There should be 9801 course categories Run the sync again – it may take some time and it does generate output. After creating all of the categories it may appear to hang – It's just commiting the transaction In my test setup (exactly as above) with a fresh Moodle installation on master, I see the following perf data: PERF: time: 87.208004s memory_total: 38125852B (36.4MB) memory_growth: 37229628B (35.5MB) memory_peak: 81938716B (78.1MB) includecount: 75 contextswithfilters: 0 filterscreated: 0 textsfiltered: 0 stringsfiltered: 0 langcountgetstring: 9807 langcountmemcache: 9804 Memory peaks at 78MB which is relatively low for such a large dataset. The number of reads/writes is regrettable, but is only high for the initial sync Try performing a second sync and you'll see far lower reads/writes and memory usage: PERF: time: 2.722942s memory_total: 39761160B (37.9MB) memory_growth: 38864936B (37.1MB) memory_peak: 57756268B (55.1MB) includecount: 75 contextswithfilters: 0 filterscreated: 0 textsfiltered: 0 stringsfiltered: 0 langcountgetstring: 7 langcountmemcache: 4 langco