Database switchover fails with “Fatal NI connect error 12637” attempting to connect to port 1523”.

Starting with NFM-P 19.11, Oracle JDBC connections use the PSH, ACK, and URG flags for connections to the Oracle database. Some customer firewalls may block connections using the URG flag, resulting in failed connections and failure to initialize the Oracle database.

Check to see if a firewall is blocking packets marked with the TCP urgent flag, which is used by Oracle. Such packets, including those for all documented destination TCP (and UDP) ports, should be allowed. See the NSP Planning Guide for more information about NSP port communication requirements.