This topic assumes that you have an existing multisystem sysplex and want to upgrade it to support more than eight systems. To operate a sysplex of more than eight systems, all systems must be at the OS/390® (or the MVS/ESA SP Version 5) level. This topic assumes that you are migrating your Version 4 systems to OS/390.

To operate a sysplex of more than eight systems, the primary sysplex couple data set must be formatted with the OS/390 format utility.

• Migration Scenario: Use the following migration scenario to upgrade your existing sysplex to support more than eight systems.
  1. One at a time, bring down the Version 4 systems in your sysplex and upgrade them to OS/390. Then, re-IPL each system into the sysplex. The system shares the same sysplex couple data set that it used prior to the upgrade. Continue in this way until each system in the sysplex is at the OS/390 level.
  2. In the meantime, use the OS/390 format utility to format a new sysplex couple data set to support more than eight systems. When all systems in the sysplex are at the OS/390 (or the MVS/ESA SP Version 5 level), introduce the new sysplex couple data set as the alternate, using the SETXCF COUPLE,ACOUPLE command. You can then use the SETXCF COUPLE,PSWITCH command to make the alternate sysplex couple data set the primary.

     At this point, the sysplex can make use of the ARM, CFRM, SFM, and WLM couple data sets.

  3. New OS/390 systems can now join the sysplex, up to the limit for which the sysplex couple data set is formatted. The limit is specified in the format utility on the MAXSYSTEM keyword of the DEFINEDS statement.
  Note the following restrictions:

  • Once the sysplex couple data set formatted with the OS/390 format utility becomes the primary sysplex couple data set, you cannot use as an alternate sysplex couple data set one that has been formatted with the SP Version 4 format utility.
  • You can no longer introduce an MVS/ESA SP Version 4 system to the sysplex.