Defining a TCP connection on z/OS

To define a TCP connection, there are a number of settings to configure.

The TCP address space name must be specified in the TCP system parameters data set, tcpip.TCPIP.DATA. In the data set, a TCPIPJOBNAME TCPIP_proc statement must be included.

If you are using a firewall, you need to configure allow connections from the channel initiator to the addresses in the channels, and from the remote connections into the queue manager.

Typically the definition for a firewall configures the sending IP address and port to the destination IP address and port:
  • A z/OS® image can have more than one host name, and you might need to configure the firewall with multiple host addresses as the source address.

    You can use the NETSTAT HOME command to display these names and addresses.

  • A channel initiator can have multiple listeners on different ports, so you need to configure these ports.
  • If you are using a shared port for a queue sharing group you must configure the shared port as well.
The channel initiator address space must have authority to read the data set. The following techniques can be used to access your TCPIP.DATA data set, depending on which TCP/IP product and interface you are using:
  • Environment variable, RESOLVER_CONFIG
  • HFS file, /etc/resolv.conf
  • //SYSTCPD DD statement
  • //SYSTCPDD DD statement
  • jobname/userid.TCPIP.DATA
  • SYS1.TCPPARMS(TCPDATA)
  • zapname.TCPIP.DATA

You must also be careful to specify the high-level qualifier for TCP/IP correctly.

You need a suitably configured Domain Name System (DNS) server, capable of both Name to IP address translation and IP address to Name translation.

Note: Some changes to the resolver configuration require a recycle of applications using it, for example, IBM® MQ.
For more information, see the following:
Each TCP channel when started uses TCP resources; you might need to adjust the following parameters in your PROFILE.TCPIP configuration data set:
ACBPOOLSIZE
Add one per started TCP channel, plus one
CCBPOOLSIZE
Add one per started TCP channel, plus one per DQM dispatcher, plus one
DATABUFFERPOOLSIZE
Add two per started TCP channel, plus one
MAXFILEPROC
Controls how many channels each dispatcher in the channel initiator can handle.

This parameter is specified in the BPXPRMxx member of SYSI.PARMLIB. Ensure that you specify a value large enough for your needs.

By default, the channel initiator is only capable of binding to IP addresses associated with the stack named in the TCPNAME queue manager attribute. To allow the channel initiator to communicate using additional TCP/IP stacks on the system, change the TCPSTACK queue manager attribute to MULTIPLE.