TCP/IP port sharing

The TCP/IP port sharing component of the z/OS® TCP/IP Communications subsystem allows multiple listeners to listen on the same combination of port and IP address.

Port sharing can be configured to distribute HTTP requests across multiple IBM® z/OS Connect servers in a single LPAR.

Note: IBM z/OS Connect servers that use a shared port must have the same APIs and services available.
Shared ports are defined by the PORT statement in the TCP/IP profile. A shared port definition reserves a specific port number to be shared by specific z/OS address space job names. Two options of the PORT statement control port sharing:
Requests are distributed by a weighted round-robin distribution method based on the Servers' accept Efficiency Fractions (SEFs) of the listeners that share the port.
Requests are distributed based on WLM server-specific recommendations, which are modified by the SEF values for each listener. Load balancing can be more efficient if you consider the status that is provided by dynamic feedback from the z/OS Workload Manager (WLM).
When you configure port sharing for IBM z/OS Connect, define shared ports for any ports that receive HTTP or HTTPS requests to invoke APIs or services. For example, define the port values specified on the httpEndpoint element with id="defaultHttpEndpoint" in your server's configuration file. For multiple IBM z/OS Connect server address spaces to share a port, their job names must start with the same characters. It is the common portion of the job name that must be specified on the PORT definition. For example, to uniquely identify two servers:
  1. Use the BAQSTRT JCL started task procedure provided in <hlq>.SBAQSAMP.
  2. Specify the JOBNAME parameters as JOBNAME=ZCHA1 and JOBNAME=ZCHA2. The common portion of the job name in this instance is "ZCHA".
Note: Use the JOBNAME parameter rather than an identifier for started tasks. See Starting a system task from a console in the z/OS MVS™ System Commands documentation. If you choose to use identifiers, be aware that it is the common portion of the identifier value that is used as the job name in the shared port definition.

Configure a separate port to handle outgoing RESTful API requests from z/OS subsystems if the same IBM z/OS Connect server is used to handle both outgoing RESTful API requests and incoming requests that access z/OS subsystems. Using separate ports allows for better security and audit control.