FICON CTC partition links

Starting with DPM R5.2, you can create FICON® CTC partition links. A FICON CTC partition link can connect only partitions that reside on the same system. These partitions use the partition link only for data transfer among the group of partitions; a FICON CTC partition link does not provide access to storage devices. The system on which the partitions reside must have FICON connections that are available to use as paths for the partition link.

When you create a FICON CTC partition link, you define the link characteristics (such as name and type); add at least two existing partitions to use the link; define the configured network paths for all added partitions to use; and define the devices that enable the added partitions to communicate through the new link. To view existing or configure new FICON connections (paths), you can use a link in the Configure Partition Links task to go to FICON CONNECTIONS, which is part of the Configure Storage task.

One advantage to using FICON CTC partition links is the ability to configure a z/VM® Single System Image (SSI) cluster to reduce the complexity of adding and managing z/VM hypervisors. With an SSI cluster in place, you can configure Live Guest Relocation (LGR) to avoid planned outages by moving Linux® virtual servers without disruption to their workloads.

For example, consider the four partitions in Figure 1.
  • All of these partitions are running the z/VM operating system and reside on the same DPM-enabled system. The z/VM operating system must be z/VM Version 7.1 or later.
  • On that system, an administrator has defined FICON connections that use the following FICON adapters: FICON 0108 A01B-04, FICON 0140 A20B-02, FICON 0109 A01B-04, and FICON 0141 A20B-02. These connections are defined as switched connections that are intended for both CTC and Storage usage, which means that these connections go through a configured fabric and switch in the storage area network (SAN), and can be used for both network traffic between partitions on the same system, and data transfer between the system and storage devices.

With this configuration, the four partitions can be interconnected through a FICON CTC partition link and can become members of a z/VM SSI cluster.

Given the configuration shown in Figure 1, an administrator uses the Configure Partition Link task to create a FICON CTC partition link, providing a name for the link and selecting the DPM-enabled system. The administrator then completes the following steps through the Configure Partition Link task.
  1. Adds the four partitions to the list of partitions that can use the FICON CTC partition link.
  2. Defines the paths to interconnect the four partitions. Only one path is required, but defining at least two paths is the suggested practice, for improved bandwidth, performance, and redundancy. The administrator defines each path, one at a time, by completing the following steps.
    1. Selects Add path to add an existing path.
    2. Through the Add path dialog, selects Switched as the type of path to add. (Other connection types are available for different use cases.)
    3. Selects the first set of adapters, FICON 0108 A01B-04 and FICON 0140 A20B-02, from the drop-down lists, and selects Add to add the path. These two system adapters are both connected to Switch A in Fabric A. When the administrator creates the partition link, a path is established from adapter FICON 0108 A01B-04 to Switch A, and back into adapter FICON 0140 A20B-02.
    4. Repeats these steps to add another path that uses a second set of adapters: FICON 0109 A01B-04 and FICON 0141 A20B-02. These two system adapters are both connected to Switch B in Fabric B. When the administrator creates the partition link, a path is established from adapter FICON 0109 A01B-04 to Switch B, and back into adapter FICON 0141 A20B-02.
    5. Selects Next to proceed to the next step.
  3. Reviews the device information associated with each added partition. Devices numbers are automatically supplied, but the administrator can change them. Figure 2 shows the sample device numbers assigned to each partition for the first path, which uses adapters FICON 0108 A01B-04 and FICON 0140 A20B-02. The device number assignment for the second path (adapters FICON 0109 A01B-04 and FICON 0141 A20B-02) is similar, except the device numbers are 4100, 4101, and 4102.

    After the administrator reviews the summary for the new FICON CTC partition link and selects Create to create it, DPM asynchronously attaches the partition link to all four partitions.

With the FICON CTC partition link defined and attached to all four partitions, it is ready for use. The paths that it provides can be used for Inter-System Facility for Communications (ISFC) based SSI communications. If any of the selected partitions are active at the time this partition link is created, you might need to use commands on the operating system of each active partition to verify that the devices are available, configure them for use, and to confirm data transfer between the connected partitions.

  • For detailed instructions about defining a FICON CTC partition link, see the New partition link: FICON CTC topic in the online help for the Configure Partition Links task. This topic includes sample z/VM commands for configuring and verifying the data transfer between active partitions.
  • For information about z/VM SSI clusters, go to the z/VM library in IBM® Documentation (https://www.ibm.com/docs/en/zvm), select the version of z/VM that you are using, and search for the topic, Setting Up z/VM Single System Image Clusters.