Dynamic I/O for a Standalone Coupling Facility Comes to z14
Brittany.Ross 50W79RR42T Comment (1) Visits (7578)
IBM has recently introduced support for Dynamic I/O for standalone Coupling Facilities on the IBM® z14™ family of servers with IBM United States Hardware Announcement 118-075
In order to enable this new feature which is performed in the IODF, we first needed to upgrade the support level to GA2 on our z14 server. Dynamic I/O for a standalone Coupling Facilities required us to introduce an LPAR that must be named “MCS_1” and reside in CSS 5 partition B. The MCS_1 LPAR is defined as a firmware partition that runs a hardware activation service that performs the dynamic change operations on behalf of HCD running on a z/OS system on a separate z14 GA2 server. When adding the new MCS_1 LPAR to our existing standalone coupling facility, the task was disruptive because it required us to POR the z14 system to initially activate the I/O configuration for the LPAR and instantiate it. Once we activated the new image on the standalone coupling facility, we could make subsequent dynamic I/O changes non-disruptively, driven remotely from a z/OS HCD system. Additionally, we found that in order to allow dynamic configuration updates for any Z servers, the ‘Allow dynamic changes to the channel subsystem input/output (I/O) definition’ option needs to be selected in the activation profile of the server. This controls whether the I/O definition established for the CPC activated by the profile can be dynamically changed. It can be turned on or off via the ‘Operational Customization -> Customize/Delete Activation Profiles’ task on the HMC/SE. Being able to set this on standalone CF servers is not new, but until now, it had no effect since dynamic I/O wasn’t possible. With the new dynamic I/O for a standalone Coupling Facilities support, this option must be enabled in the activation profile that is used to POR the server.
Software solution APARs we added to the z14 server that has z/OS images running HCD on top of running GA2 support are:
As always, check out the appropriate PSP bucket (for example, see the Upgrade 3906DEVICE bucket for the latest z14 support) to get the latest supported APARs for this solution when you’re ready to take advantage of the support yourself.
To make I/O configuration changes to the standalone coupling facility, we had to modify our IODF in a “driving” z/OS system using either HCD or using the Hardware Configuration Manager (HCM), the same way we had done prior to the introduction of this feature. Using this feature, we were able to make any I/O change to our standalone coupling facility. For example, we were able to dynamically add and remove all supported coupling link types (such as CIB 1x, CIB 12x, CS5, and CL5) from our coupling facility partitions. When removing CHPIDs from our standalone coupling facility using the dynamic I/O feature, the CHPIDs were able to remain online, unlike our CECs running z/OS images, which require all CHPIDs be configured offline prior to the dynamic I/O change. This was possible as long as we specified that hardware deletes were allowed and should be forced offline when activating the new hardware configuration for the standalone coupling facility.
With the new support, three new options have been added to the 'Actions on selected CPCs' HCD menu that appears when selecting a CPC from the 'Processor Cluster List' (option 2.11 from the HCD main menu). The new options allowed us to activate hardware-only changes on the selected CPC, view the current active configuration, and download the active configuration. Below is a screenshot of the aforementioned menu and the new options that appear:
Option 5 from the ‘Actions on selected CPCs’ menu (Activate hardware changes only) is how we initiated dynamic I/O for our standalone coupling facility. We found that the activation of the IODF on z14 standalone coupling facility running GA2 support MUST be driven from an image on a z14 system running the support level (GA2). We learned this after an attempt to activate the IODF on our standalone coupling facility from a z13 server without realizing we were using an unsupported system. We came to the conclusion that trying to dynamically activate an IODF on a standalone coupling facility from a z14 GA1 server or earlier will fail. Once the hardware activate is submitted, a message list dialog is displayed on screen. This message list allowed us to review the results of the activation. For example, if the hardware activation on the standalone CF is successful, the following message was displayed:
Once the IODF activation completes, we always wrote out the IOCDS as we always do, using option 1 from the ‘Actions on selected CPCs’ menu. This is important so that the IOCDS is up-to-date with the latest changes, in the event that the target standalone coupling facility CEC has to do a POR or IML for any reason in the future.
After taking the one-time setup outage to add the MCS_1 LPAR to the coupling facility, we were able to easily update the IODF configuration of our standalone coupling facility system without disruption to the coupling facilities residing on it or to the rest of our environment. Furthermore, unlike our environment, a business with a configuration that is dependent on standalone coupling facilities may no longer have to worry about the cost and maintenance of a small software LPAR running HCD on their standalone coupling facilities. The new dynamic I/O for standalone coupling facility feature released for IBM’s z14 GA2 is essential for any company who has a standalone coupling facility in their enterprise infrastructure.