16191, 0000, "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.