Hello @svk,
welcome to the community of Nextcloud 
You started a topic in support category. Unfortunately you ignored the template and a lot of information to help you is missing. Please edit your original post and add all required details like Nextcloud version, webserver type and version, os version, related log file content. Use the support template.
Without additional information the community members cannot help you.
a major issue from your snippet is an issue with DB access
Regards,
wwe