Database reach max process or sessions, son no new login is available, first your sysadmin cant access too for solve the problem seting new process value, is a production enviroment so we dont want to kill the instance as a first step to solve the problem .
Flash recovery area full? Backups fail in delete archives after backup?
with this error
RMAN-08137: WARNING: archived log not deleted, needed for standby or upstream capture process
The root problem is in standby or oracle streams not working properly
you should check first if you can investigate because the problem not yet rise
a urgent service problem with any outage of resources.