When there is a big installation with many frontends and a single DBMS server (even if it is a cluster) the most critical factor we observed for the scalability of the system is the number of requests done (in reading mode) to the table

{prefix}config: almost every page requires to include these information.

So, based on the availability of a local filesystem area on each front-end (web server Apache), we developed a slight modification of the code to store in a local file the JSON representation of the actual configuration settings (the main modification is in the file lib/setuplib.php : lines 588-677 of attached code).

The modification could be activate trough the usage of a subfield of the dboption property in the CFG object, created starting by the config.php file.

The modification also includes a small change in a single file of admin directory (admin/settings.php : lines 39-44), in order to flush this cache when data is saved in the {prefix}

config.

Our modifications are based on the 2.0.1 versione of the code, but should be possible to apply it to almost all the version of Moodle available, as far as I have the possibility to check (maybe on 2.2 should be checked, I haven't done it, right now).

We tested it with Oracle 10g, but maybe could laso help with other DBMS, and it seems to us it improves quite a lot the speed-up for page loading, even on a single server...

Hope this could help, regards from the staff of eLab at USI/SUPSI - Switzerland http://www.elearninglab.org/