IBM z/VM 7.4 CP Change Log

Last Updated: 6 May 2025

Service and feature packs released for the z/VM 7.4 CP component

z/VM 7.4 introduced linear service to the product. Service fix packs and feature packs are now released on a regular cadence. By installing the latest pack you will receive all service fixes and features for the component. Refer to the change log table below for a comprehensive list of changes to the component since the z/VM 7.4 General Availability date.

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A list of service for z/VM 7.4 CP
Release	Level	Available	Type	Crit PE	Security	HIPER	APAR	PTF	Details
7.4	0101	20250502May 2, 2025	Hot fix	Yes	No	Yes	VM66839	UM90524	z/VM 7.4 CP Hot Fix - Feature 01 Fix 01 Update May 6, 2025 - Critical PE introduced with this hot fix. More information INCORRECT OUTPUT FROM DIAG26C SUBCODE 20 Diagnose 26c subcode 20 for response formats 0000 0001 thru 0000 0005 can return VSWITCH information structures with an incorrect structure counter. The diagnose is provided by the invoker with a response buffer. If the response can only partially fit in the response buffer then return code 16 is returned along with the size of the required buffer. In the identified issue, the last VSWITCH structure is the same size as the response buffer. A good return code is provided but the response data contains an incorrect value. May 6, 2025 Update: A critical PE has been found due to this change. Do not install PTF UM90524 until a hot fix is provided. ACTIVE SERVER ON VSWITCH WITH HIGH RX DISCARD RATE CP QUERY VSWITCH DETAILS indicated a steady increase in RX Packet Discard count for one user with no clear explanation. After implementing RedHat OCP on zVM the customer noticed significant increases in the number of RX Packets Discarded for the server responsible for managing several other dependent servers. A review of the dropped packets collected via TRSOURCE type LAN trace revealed that these were overflow packets. Most packets were being discarded in sets of (approximately) 1000 packets. The timing of these events lined up with startup times for one or more dependent servers. This normally suggests the presence of a resource constraint affecting the receiver, but monitor data revealed no significant problem in that area. UNEXPECTED FORCE ARCH REQUIRED FOR LGR Customers applying VM66819 APAR across an SSI would eventually need to issue FORCE ARCH relocations to move virtual machines from systems without the APAR applied back to systems that do have VM66819 applied. The problem was caused by the changing of an internal system value (SYSMAXD) between processors. VARIOUS ABENDS SYSTEM ITERATOR SERIALIZATION ISSUE Hiper related - In the iterator, there was an underlying assumption about how to check the table level using STEs that was not correct. This error can cause various abends. We now obtain the table level info from elsewhere. This affects all configurations. PRG004 ABENDS Hiper related - Fix to resolve a rare situation when a guest does not respond to IUCV *MONITOR sample notifications. Prior to the fix, a PRG004 failure may occur.
7.4	0100	20250403April 3, 2025	Feature pack	No	No	No	VM66829	UM90510	z/VM 7.4 CP Feature Pack - Feature 01 Fix 00 More information TRSOURCE IO 5-Digit Device Support Extends TRSOURCE support to 5-digit device addresses, which comprise a subchannel-set (SS) number concatenated to the left of the device address. This applies only to real device addresses and therefore to the operand of the TRSOURCE command RDEV keyword. This support has also been added to the DVF component and is available in APAR VM66830. Two-Speed Monitoring Two-Speed Monitoring provides a mechanism for collecting z/VM Monitor data at two different sampling rates. This avoids disrupting existing client processes that rely on Monitor data collection.
7.4	0008	20250325March 14, 2025	Fix pack	No	No	Yes	VM66831	UM90506	z/VM 7.4 CP Fix Pack - Feature 00 Fix 08 More information System Hang Due to MDC Consuming Less than 2G Storage Logic is added to consumers of MDC frames to examine the ratio of MDC frames <2G to >2G and if skewed <2G then attempt to get a FRMTE conditionally from the >2G available zones. If this request fails, then the old path is used. This ensures a balance of MDC frames and no loop possible.
7.4	0007	20250225February 25, 2025	Fix pack	No	No	Yes	VM66821	UM90503	z/VM 7.4 CP Fix Pack - Feature 00 Fix 07 More information Unable to Detach CPOWNED Volume Marked Shared The logic to dictate whether a device can be detached or not based on CSE sharing still exists, causing unexpected denial of a DETACH command. This fix removes the check and prevents the DETACH denial when a non-SSI system attached device finds itself with spool extents that are not owned by its system.
7.4	0006	20250131January 31, 2025	Fix pack	No	No	No	VM66819	UM90502	z/VM 7.4 CP Fix Pack - Feature 00 Fix 06 More information Guest Relocation Incompatibility Internal handling of the architected value of interest was updated to prevent the relocation errors related to potential architectural incompatibility introduced to the guest. March 20, 2025 Update: When fix is applied in an SSI, "FORCE ARCH" is still required for relocations. Unplanned Hyperswap on Subchannel Offline Device To ensure this incorrect HyperSwap trigger no longer occurs, a set of changes were made to improve the CC3 error recovery path and prevent subchannel offline (SUBCHOFF) devices from persisting in a GDPS environment enabled for HyperSwap auto-quiesce. PRG006 Encountered Due to Improper Instruction Input Once it was discovered the wrong input was being passed to the failing instruction, the input was fixed. The problem situation was recreated with and without the fix to ensure the abend was avoided.
7.4	0005	20241218December 18, 2024	Hot fix	Fixed	No	Yes	VM66815	UM90496	z/VM 7.4 CP Hot fix - Feature 00 Fix 05 More information PE Corrected with this Fix Pack This fix removes the "System Hang Due to MDC Consuming Less Than 2G Storage" code that was part of fix pack 0004 and restores the previous function.
7.4	0004	20241014October 14, 2024	Fix pack	Yes	No	No	VM66800	UM90483	z/VM 7.4 CP Fix Pack - Feature 00 Fix 04 Update Nov. 25, 2024 - PE introduced with this fix pack. More information System Hang Due to MDC Consuming Less Than 2G Storage Logic was added to subroutine HCPPTG:GetFRMTEs that will rebalance the distribution of MDC data frames by looking at the current distribution and preferring frames >2G when the current distribution is skewed toward <2G memory. November 19, 2024 Update: A critical PE has been found due to the change in the HCPPTG:GetFRMTEs subroutine. A MCW002 ABEND may occur during normal systems operation (replenishment of the uncleared local available lists) on a system that is paging or near paging. RDM024 ABEND After Clearing SSI Slot With Dummy ARD The ARD comparison routine was changed to give the correct equality result when two dummy ARDs are compared. PEVM66675 Missing Interrupt for Dedicated PCI Function PCI function interrupt processing code was modified to not alter adapter interrupt summary bits for dedicated PCI functions. This will prevent missing interrupts for the owning guest. ABENDLCK001 HCPLCK+DC8 After NVME EDEV Lost An incorrect invocation of the z/VM interrupt handler for NVMe EDEVICES was used when the interruption presented for the PCI Function removal was received. This call to the NVMe interrupt handler has been corrected.
7.4	0003	20240928September 28, 2024	Fix pack	No	No	Yes	VM66796	UM90478	z/VM 7.4 CP Fix Pack - Feature 00 Fix 03 More information SXA004 ABEND (ABENDSXA004) caused by the CP CHANGE or CP TRANSFER Commands CP CHANGE and CP TRANSFER commands were failing to release storage obtained to hold the user's DVMD when running in a cross system SPOOL (SSI cluster) environment. CP SPOOL Processing Causes DirMaint Message Flood The problem is in the spool TRANSFER and CHANGE command processing in an SSI cluster. Specifically, the problem occurs when a TRANSFER or CHANGE command is issued for a file a user owns that is a copy file on the member where the user is logged on. When the file is moved between spool device queues (rdr to prt/pun or prt/pun to rdr) but the owner of the file is not changed, the file ends up in a bad state. The command response indicates the file was transferred but it only happens on the file's originating member and not on the copy member. This leads to further unexpected behavior of other spool commands such as QUERY RDR/PRT/PUN, QUERY FILES and PURGE. VARY Hangs After Unplanned Hyperswap Reports of users experiencing VARY command hangs and other similar external symptoms which were due to stalled I/O queues where z/VM had quiesced the associated control unit for summary unit check (SUC) recovery. I/O requests are issued during the recovery process for unit checks associated with the suspension of PPRC/Metro Mirror relationships for DASD devices. During this recovery, I/O requests on the associated control unit are quiesced to allow this recovery to complete and the condition is then reset. It was determined that some of this related recovery I/O could be deferred and issued after the control unit quiesce has been reset. This would allow the I/O subsystem for the control unit to be returned to normal operation as soon as possible.
7.4	0002	20240920September 20, 2024	Hot fix	No	Yes	No	VM66795	UM90474	z/VM 7.4 CP SECURITY APAR - Feature 00 Fix 02
7.4	0001	20240920September 20, 2024	Fix pack	No	No	Yes	VM66780	UM90463	Initial fix pack that is provided with the z/VM 7.4 GA installation media. More information ABEND PRG004 in ISFC Timeout Processing ISFC Serialization was expanded to account for the potential interaction between the Link I/O layer and message queue handling which led to the abend. MAC Table Synchronization Errors Following VMRELOCATE SSI communication used to indicate changes in MAC address usage was updated to ensure the guest LOGOFF case builds a valid request which will update the MAC tables on all members of the SSI. ABEND PRG004 in HCPSWL for Multi-VSWITCH LAG Configurations The processing of the state change notification received from the OSA adapter was updated to verify the network connection for the port is still operational before attempting recovery. If the port is no longer operational, there is no need to process the state change and it will be discarded. XFS File System Errors After HPF I/O to Virtual HyperPAV Alias HPF I/O translation was updated to ensure internal control block structures for virtual HyperPAV aliases are updated prior to I/O translation. This ensures the I/O requests are now always translated correctly for the current alias usage.

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