Steps for defining a LUNS and a LUNR

If your environment uses multiple Telnet servers running on a single system or in a sysplex, you can designate one Telnet server to be the LU name server (LUNS). The LUNS ensures that LU names are unique among your Telnet servers, managing LU name assignments.

Perform the following steps to configure an LU name server (LUNS) or an LU name requester (LUNR):

1. On the XCFGROUP statement block on the TELNETGLOBALS statement block, define the level of participation in the Telnet XCF group and in shared LU name management.
   • Specify the NOJOIN parameter (or do not include the XCFGROUP block) if this Telnet server should not join the Telnet XCF group. If you specify NOJOIN (or omit the XCFGROUP block), the server is not included in the XCF,GROUP display and does not allow the definition of shared LU group objects.
   • Specify the JOIN parameter if this Telnet server should join the Telnet XCF group. JOIN is the default if you code XCFGROUP. If you specify JOIN or it is in effect by default, the server is included in the XCF,GROUP display that is issued by any other XCF Telnet server; the server has LUNR capability and supports shared LU group objects. With additional XCFGROUP statements, the server can have LUNS capability.
2. Determine whether you need to partition your Telnet server sysplex into Telnet subplexes.
   • If you are not partitioning your sysplex into subplexes, do not code the SUBPLEX parameter on the XCFGROUP statement. All Telnet servers in the sysplex that participate in shared LU name management join the default Telnet XCF group EZZTLUNS.
   • If you are partitioning your sysplex, configure the SUBPLEX parameter with a suffix that is 1 - 4 characters in length. The specified suffix is right-aligned and overlays the end of the string EZZTLUNS to form a unique subplex string. For example, if the suffix value is 23, Telnet joins XCF group EZZTLU23.
3. Determine the frequency with which you want to monitor the health of the Telnet LUNS and LUNR. Use the XCFMONITOR parameter to set the frequency. At the specified time interval, Telnet checks the health of the LUNS, LUNR, and XCF Telnet tasks, and checks the health of the connection between the LUNS and LUNR. If any of these tasks or the connection appear to be unresponsive, message EZZ6099I is issued and the X indicator is set under the PDMON column in the XCFGROUP display. No action is taken by Telnet to correct the issue. A short time value can lead to false indications in a busy system. A long time value might not provide feedback quickly enough so that you can take appropriate action. The default value is a good compromise between these two possibilities.
4. To configure a LUNR, perform the following steps:
   1. Configure the following parameters on the XCFGROUP statement:
      • CONNECTTIMEOUT: You can use this parameter for a LUNR only. Specify the length of time that a LUNR attempts to establish a connection to the LUNS before quiescing its LUNR capabilities. If the CONNECTTIMEOUT time elapses and the LUNR has not been able to connect with the LUNS, then the LUNR drops all connections that are waiting in negotiation for an LU name and quiesces all ports that have shared groups. Dropping connections that are in negotiation state enables the client to try again to connect to Telnet. Quiescing the port alerts a distributor that it should send requests to other working Telnet LUNRs. When the client connection is dropped and the client reconnects to the distributor, the connection is directed to a working LUNR. When the LUNS-LUNR connection is established, the port is automatically resumed and new client connections are again routed to this LUNR. Setting the CONNECTTIMEOUT time to 0 causes client connections to remain in LU name negotiation until LUNS-LUNR communication is established.
      • RECOVERYTIMEOUT: You can use this parameter for a LUNR only. Specify the length of time that the LUNR attempts to establish a connection when the LUNS is in RECOVER state before dropping active client connections that have shared LU names assigned to them. A new LUNS in RECOVER state cannot become active until it has received updates from all LUNRs that have shared LUs that are in use. If a LUNR cannot communicate with the LUNS during recovery time and the LUNR has shared LUs assigned, then the LUNS cannot become active and none of the LUNRs are able to receive LU name assignments. If the LUNR drops all active client connections with shared LUs, then the LUNS is alerted through XCF that the LUNR no longer owns shared LUs, and the LUNS can then become active.
   2. Define the shared LU groups for the LUNR. Use the SLUGROUP and SPRTGROUP statements to define the shared LUs.
5. To configure a LUNS, specify LUNS on the XCFGROUP statement and configure the following parameters on the LUNS statement:
   • ipaddr port: Specify the IP address and port on which the LUNS will listen for its administrative connection to communicate with LUNRs.
   • PRIMARY or BACKUP: Specify whether this Telnet server is a primary LUNS or a backup LUNS.
   • RANK nnn: Specify the start rank of this LUNS, relative to others, when this LUNS is in standby mode and the active LUNS fails.