How to Clear Apache Cache?

cd $OA_HTML/_pages
rm -rf oahtml
mkdir oahtml

$ rm * $COMMON_TOP/_pages (for 11.5.10 and above)
$ rm * $OA_HTML/_pages/_oa__html (for 11.5.5 - 11.5.9) 

Note:- The best practice is to stop Apache, issue the rm command, then start Apache. 

See ML Notes 472731.1, 471763.1 and 295484.1.
You need to stop apache before executing the rm commands, then start up apache