Db2 configuration with TCP/IP

The Db2 subsystem uses different TCP/IP ports to do different tasks.

  • As a requester, Db2 uses an ephemeral port. You do not need to specify this port.
  • As a server processing TCP/IP connection requests for DRDA SQL applications, Db2 uses a server port or the well-known port, 446, which is used for relational database communications.
  • A server resynchronization port is used for processing 2-phase commit resynchronization requests.

This requires some planning because the port number is used to pass the network requests to the appropriate Db2 subsystem. Each location must have a unique port number.

The figure below shows some typical z/OS® system configurations.

  • SYSTEM1 contains only one Db2 subsystem, so the DRDA well-known port (446) can be assigned to Db2. In the example, port number 5020 is assigned for 2-phase commit resynchronization.
  • SYSTEM2 contains two Db2 subsystems, so it is impossible to assign the port numbers 446 and 5020 to both Db2 subsystems because TCP/IP can only support one server at each port number. The problem is resolved by assigning the 446 and 5020 port numbers to DB2C, and port numbers 5021 and 5022 to DB2D.

Be sure to consider the impact of future system consolidations. If SYSTEM1 and SYSTEM2 are consolidated so that DB2A, DB2C, and DB2D run on a single z/OS system, you must take special precautions because DB2A and DB2C have the same TCP/IP port numbers. You can resolve this conflict by changing the port numbers of either DB2A or DB2C to eliminate the duplicate port numbers.

Figure 1. Typical z/OS configurations
Begin figure description. A figure shows the typical z/OS system configurations, as discussed in the text above. End figure description.