Thread:Project:Support desk/cannot upgrade to 1.18 from 1.17 - APC issue/reply (4)

Yes, $wgMainCacheType = CACHE_ACCEL; means use either APC, XCache or WinCache. If you don't actually have such a program installed, MediaWiki will error if you try to force it to use such a program. CACHE_ANYTHING means mediawiki will auto-detect what type of cache you have. If all else fails, it will cache things in the db (which might actually be slower then not caching stuff at all. The default config is to have $wgMainCacheType set to CACHE_NONE, but the parser cache and message cache [which cache expensive things] to use CACHE_ANYTHING)