IBM zSeries and IBM Z platform considerations

IBM Zz/OS® and zSeries environments support the following:
  • More than 15 logical partitions. Only LPAR mode is supported; you cannot run in basic mode on these processors.
  • Multiple logical channel subsystems, which allow you to logically partition your physical channel resources to accommodate large-scale enterprise workload connectivity and high bandwidth demands. Each logical channel subsystem can have up to 256 CHPIDs and 15 logical partitions. See "Machine limits and rules" in the IOCP User's Guide for limits on a number of logical partitions in a logical channel subsystem.
  • In each channel subsystem, besides subchannel set 0, there are additional subchannel sets (SS), starting from SS1. The number of additional SSs is processor dependent and documented in "Machine limits and rules" in the IOCP User's Guide. For additional information on defining subchannel sets, see Defining multiple subchannel sets.
  • Channels can be shared, or spanned, across logical channel subsystems. Spanned channels allow you to minimize the number of physical CHPIDs, switch ports and cables required. Channels that would otherwise be under-utilized could have their utilization increased by spanning them across logical channel subsystems. See Defining spanned channel paths for more information.
  • On an IBM® System z9® or later processor, you have maximum number of device parameters for each subchannel set that may be used by your installation. HCD defaults the maximum numbers to 63.75K for SS0 and to Start of change64KEnd of change for other available SSs.
  • You can also disconnect the partition from any assigned resources using dynamic I/O. The partition will revert back to being a reserved logical partition — the space used by the partition is not returned to the available pool of storage. See Dynamically changing logical partitions to the I/O configuration for more information.