We upgraded Moodle system from 3.3 to 3.4 last month.
We also upgrade PHP from 5.6.x to 7.0.29 version and MySQL to 5.7.x version.
Opcache function is also enabled in PHP to improve peformance.
After new semester started, I find Moodle system is loaded improperly.
Last week, it show "system error and cannot open <<moodle root>> file...."
Today , it show "programming error and please inform admin to fix it...."
I just stop apache web server and startup again to resume service.
it worked for one week.
It seems it is relevant to the opcache cannot load the file to cache properly.
now opcache setting in php.ini is as the following.
opcache.enable = 1
opcache.use_cwd = 1
opcache.validate_timestamps = 1
opcache.save_comments = 1
Please advise what the problem is .