If you are getting this error in cpanel when trying to look at the mysql databases:
Mysql::initcache() failed: The adminbin “cpmysql” in the “Cpanel” namespace call to function “DBCACHE” ended prematurely: The subprocess reported error number 255 when it ended.
https://forums.cpanel.net/threads/the-mysql-server-is-currently-offline.474561/
“WHM » Server Configuration » Tweak Settings » SQL » Use INFORMATION_SCHEMA to acquire MySQL disk usage” Set that to OFF then it should work after that.