Reserving the DRDA port

If a member of a data sharing group is restarted on another LPAR, the TCP/IP on that system must be configured to allow the member to use the DRDA port.

To ensure this, reserve the DRDA port on each system for the Db2 DDF address space by assigning the port to every member that could conceivably start on that system. By explicitly assigning this port, you prevent other programs from using the DRDA port number.

On each system, replicate the TCP/IP PORT configuration profile statement shown here:

PORT
⋮
  446 TCP DB1ADIST SHAREPORT
  446 TCP DB2ADIST SHAREPORT
  446 TCP DB3ADIST SHAREPORT
  446 TCP DB4ADIST SHAREPORT

Recommendation: Specify the SHAREPORT option, as shown in the TCP/IP PORT configuration profile statement. Specifying this option configures TCP/IP to allow multiple listeners on the DRDA port (port 446). As client connection requests arrive for this port, TCP/IP distributes them across the members. TCP/IP selects the member with the fewest number of connections (both active and queued) at the time that the request is received.

The member chosen by TCP/IP receives all of the DRDA server's workload for that TCP/IP instance, leaving the other members with no TCP/IP server threads for DRDA. This is transparent to the DRDA clients if the member that is processing the TCP/IP requests does not reach the MAX REMOTE CONNECTED thread limit. If this limit is reached, the client's connection request is rejected.

Tip: After you resolve a failure situation, move the member back to its original CPC.