If you have installed mediawiki, you might have seen this error, then again you might not have seen it because it only occurs when you attempt to cache the results.
Parsing the wiki is something of a processor and memory intensive task. The database for some of the mediaviki projets like the wikipedia is just huge and runs into giga bytes, so caching is a good option. In order to make it work you need to edit DefaultSettings.php. The comment at the top of the file forbids it but go ahead and do it anyway.
The changes are:
$wgShowIPinHeader = false;
$wgUseFileCache = true;
$wgUseGzip = false;
That’s half the job one then you have to change into the directory where the wiki scripts are installed and then type
mkdir -p upload/cache
chmod 777 upload -R
Now the sofware will attempt to save the processed page on the hard disk whenever possible. Some pages (for example – the edit or history pages) cannot be cached.
