IBM z/VM 7.3 Preview

Last Updated: 5 April 2022


Planned availability date - Third quarter, 2022

z/VM 7.3 will provide IBM clients with the premier hypervisor on their modernization to hybrid cloud for hosting enterprise-class virtual servers to exploit the IBM Z and LinuxONE advantages in scalability, performance, high availability, and security.

The objective of z/VM 7.3 is to enhance the proof points on their modernization to hybrid cloud, specifically those associated with scalability and efficiency. z/VM is designed to enable the deployment of up to thousands of Linux servers on a single IBM Z or LinuxONE server.

While cloud computing has become the standard use model for IT services, an IT infrastructure continues to be the foundation of every IT service. Realizing the benefits of cloud computing requires an infrastructure such as z/VM that delivers availability, reliability, security, and performance, while also providing strong virtualization technology.

Virtualization is fundamental to delivering infrastructure as a service (IaaS), the basic building block for cloud. IBM continues to invest in z/VM technology to provide leading-edge virtualization capabilities. This progression can meet the needs of IT organizations to deliver the foundation for user satisfaction on both types of workloads:

  • Cloud-native workloads based on Red Hat OpenShift Container Platform and IBM Cloud Paks or other container technologies
  • Noncontainerized workloads deployed in a cloud or traditional environment from IBM such as IBM WebSphere, open source such as MongoDB, or software from ISVs

z/VM, together with IBM Cloud Infrastructure Center that helps to manage the lifecycle of virtual infrastructure, provides the foundation for private cloud on an IBM Z and LinuxONE server as part of a hybrid cloud approach.

z/VM virtualization technology enables the deployment of more virtual servers, for both noncontainerized and cloud-native workloads, in a single IBM Z or LinuxONE server than any other platform through legendary scalability, system management, and performance. z/VM supports the following guest operating systems: Linux, IBM z/OS, IBM z/VSE, IBM z/TPF, and z/VM itself, as well as Red Hat Enterprise Linux CoreOS as a part of the Red Hat OpenShift Container Platform. In addition, the z/VM hypervisor helps ensure continuous infrastructure availability by tightly integrating with IBM GDPS resiliency-focused offerings and Live Guest Relocation support.

With z/VM 7.3, IBM continues to deliver enhancements to its z/VM advanced virtualization technology on IBM Z and LinuxONE servers using the z/VM continuous delivery (CD) model. This CD model for new function offers clients timely support for new technology throughout the life of a z/VM product release using a delivery mechanism that is familiar to clients and time tested. The z/VM CD model allows schedule flexibility as IBM partners with the z/VM community in the design, development, and delivery of new functions that are not centered around a specific release date.



The following enhancements are included in z/VM 7.3:

  • 8-member SSI support. Increases the maximum size of a Single System Image (SSI) cluster from four members to eight, enabling clients to grow their Single System Image (SSI) clusters to allow for more workload and providing more flexibility to use live guest relocation (LGR) for nondisruptive upgrades and workload balancing.
  • NVMe emulated device (EDEVICE) support. Enables NVMe devices connected through PCI Express (PCIe) adapters to be defined and managed as Fixed-Block Architecture (FBA) EDEVICEs. As such, all host and guest FBA functions are supported except for those that require stand-alone support such as Warm Start and Checkpoint. Linux guests exploiting EDEVICEs defined on NVMe adapters are not eligible for LGR. NVMe Adapters are only available on LinuxONE servers.
  • Up to 4 TB of memory per LPAR. This new function was delivered in the service stream of z/VM 7.2. A fully configured 8-member SSI can address up to 32 TB on a single IBM Z or LinuxONE server, or 32 TB across multiple servers along with up to 80 logical processors (40 when Simultaneous Multi-Threading (SMT) is enabled) supported on each member.
  • Dynamic Memory Downgrade. This new function was delivered in the z/VM 7.2 service stream, and it provides the added flexibility of moving LPAR memory from one or more z/ VM system images to one or more other z/VM system images running on the same physical server. This can help clients to nondisruptively align their hardware assets with shifting workload demands across their z/VM system images if they are in an SSI cluster or in separate z/VM LPARs. This may prove particularly useful when moving running virtual machines from one SSI member to another using LGR.
  • New Architecture Level Set (ALS). z/VM 7.3 includes an ALS that requires an z14 server and higher.
  • External Security Manager interface enhancements. These interfaces have been enhanced to allow control of the CP DEFINE MDISK command. These interfaces are exploited by IBM RACF/VM and enable a z/VM security administrator to restrict and audit all means of creating a minidisk.
  • System default changes:
    • Default password for User Directory

      New with product install, z/VM 7.3 provides the ability to select a default password when installing or upgrading a z/VM system

    • User Directory TODENABLE

      Some capabilities that previously required OPTION TODENABLE in the user's directory definition will be standard for all users in z/VM 7.3. Specifically, all virtual machines on z/VM 7.3 will be able to alter their virtual time-of-day (TOD) clocks using the SET CLOCK instruction. In addition, class G users no longer need TODENABLE to set the virtual clock to a specified value using the SET VTOD command with the DATE, TIME, and SYSTEM options. TODENABLE is still required for the FROMUSER and MSGPROC options of SET VTOD, which involve access to another virtual machine's clock.

    • TCP/IP configuration statement changes

      In z/VM 7.3, the NOUDPQUEUELIMIT option of the ASSORTEDPARMS statement is being replaced by a new UDPQUEUELIMIT configuration statement. This new statement will allow a numerical limit to be specified for the maximum number of incoming datagrams queued on a UDP port. The default limit is 20 datagrams. If 0 is specified, there will be no limit, which is the equivalent of NOUDPQUEUELIMIT. The NOUDPQUEUELIMIT option will still be accepted in z/VM 7.3 but UDPQUEUELIMIT takes precedence. In addition, the FOREIGNIPCONLIMIT default will be changed to a set value of 256 and will no longer be based on the initial TCBPOOLSIZE.

    • Change in location and size of the MONDCSS and PERFOUT saved segments

      The default CP MONITOR MONDCSS saved segment starting virtual address has been changed to 1 GB and the size has been increased to 96 MB. The IBM Performance Toolkit PERFOUT saved segment starting virtual address has been changed to 1120 MB, immediately following the new MONDCSS. The reasons for these changes include:

      • Moving the segment starting locations addresses a problem with the Linux kdump configuration, which failed in a virtual machine with 1 GB of virtual memory that had attached one or both current versions of these segments.
      • Increasing the size of the MONDCSS segment accommodates the increased volume of CP Monitor data produced and provides room for its future growth.
        These changes will not affect existing versions of these segments; they must be recreated for the new defaults to take effect.
  • Support for the IBM z16 Model A01 servers includes:
    • Guest enablement to exploit the following functions:
      • Imbedded Artificial Intelligence Acceleration is designed to reduce the overall time required to execute CPU operations for neural networking processing functions and help support real-time applications like fraud detection.
      • Compliance-ready Central Processor Assist for Cryptographic Functions (CPACF) counters support allows guests to track crypto compliance and instruction usage.
      • Breaking Event Address Register (BEAR) enhancement facility improves the ability to debug wild branches.
      • Vector Packed Decimal Enhancements 2 delivers new instructions intended to provide performance improvements.
      • Reset DAT Protection Facility provides a more efficient way to disable DAT protection, such as during copy-on-write or page change tracking operations.
      • Support for the Consolidated Boot Loader provides guest IPL from a SCSI LUN. Note: Guest IPL from SCSI, with or without the DUMP option, will now require a minimum guest virtual memory size of 768 MB.
      • The RoCE Express3 adapter allows guests to exploit Routable RoCE, Zero Touch RoCE, and SMC-R V2 support.
      • The Crypto Express8S (CEX8S) adapter is supported as a dedicated or shared resource. Dedicated guests will be able to take advantage of all functionality available with the CEX8S adapters, including assorted new enhancements and use of Quantum Safe APIs.
      • Support for CPU and Core topology location information will be included in z/VM monitor data, providing a better picture of the system for diagnostic and tuning purposes.
      This support is available for z/VM 7.1 and 7.2 with the PTF for APAR VM66532
    • The following infrastructure support must be installed on all members within a z/VM SSI cluster before any member of the cluster is IPLed on an IBM z16 server:

      • z/VM 7.3
      • z/VM 7.2 with the PTF for APAR VM66504
      • z/VM 7.1 with the PTFs for APARs VM66206 and VM66504

      For further information on z/VM support of the IBM z16 server, see the z/VM IBM z16 required service web page and the IBM Support - Preventive Service Planning bucket Upgrade 3911DEVICE, Subset 3911/ZVM.

    • z/VM Continuous Delivery model

      IBM will deliver most new z/VM 7.3 function as new function APARs in the service stream. When z/VM 7.3 becomes available, z/VM 7.2 will, with a few exceptions, receive only corrective service. Similarly, when a new release is introduced after z/VM 7.3, new function APARs will be delivered on that release and 7.3 will receive mostly corrective service only.

      The following z/VM 7.2 enhancements delivered during 2021 will be in the base of z/VM 7.3, providing additional IBM z16 benefit for z/VM workloads:

      • 4 TB Real Memory support - With the PTF for APAR VM66173, support for up to 4 TB of real memory will allow z/VM systems to address a full 4 TB of first-level (real) memory, doubling the previous supported limit of 2 TB.
      • Dynamic Memory Downgrade support - With the PTF for APAR VM66271, Dynamic Memory Downgrade extends the real storage dynamic management characteristics of z/VM by allowing up to 50% of the real memory to be removed from a running z/VM system. A minimum hardware bundle level is required to avoid a possible downgrade stall. For additional details, see the Dynamic Memory Downgrade information web page.
      • Improved LGR for shared crypto users - With the PTF for APAR VM66496, LGR for APVIRT shared crypto environments is enabled when the type of shared crypto resource on the source system does not match the type on the target system.
      • z/Architecture Extended Configuration (z/XC) support - With the PTFs for APARs VM66201 (CP), VM66425 (CMS), and VM66489 (Performance Toolkit), CMS applications that run in IBM z/Architecture can use multiple address spaces. Programs can use z/Architecture instructions and registers, within the limits of z/CMS support, and can use VM data spaces in the same CMS session. IBM z16 requires z/CMS and z/XC support to be configured within guest virtual machines that exploit z/VM HCD support. In addition, when the PTF for IOCP APAR VM66549 is applied, z/CMS support is required to be configured on any IBM Z orLinuxONE server. IOCP support is in the base of z/VM 7.3 and requires z/CMS.
      • Direct to Host Service Download support - With the PTF for APAR VM66540, z/VM 7.2 provides an optional way to download service to your z/VM system. A web interface simplifies the downloading of z/VM service that was ordered through IBM Shopz. The service files can be transferred through direct-to-host connection.


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