ORA-16191: Primary log shipping client not logged on standby
Cause: An attempt to ship redo to standby without logging on to standby or with invalid user credentials.
Action: Check that primary and standby are using password files and that both primary and standby have the same SYS password. Restart primary and/or standby after ensuring that password file is accessible and REMOTE_LOGIN_PASSWORDFILE initialization parameter is set to SHARED or EXCLUSIVE.