IBM Support

Customers running zHyperLink write with FlashCopy may experience undetected data loss on the FlashCopy target volume.

Notification


Risk classification

HIPER (High Impact and/or Pervasive)

Risk categories

Data Loss

Affected Domain

DS8900F and DS8A00 systems using zHyperLink write with FlashCopy

Abstract

Customers running zHyperLink write with FlashCopy may experience undetected data loss on the FlashCopy target volume.

Description

Customers running zHyperLink write with FlashCopy may experience undetected data loss on the FlashCopy target volume, if a FlashCopy Establish command is executed in the small window between when a zHyperLink write operation starts and completes. The FlashCopy source volume is not affected.  FlashCopy on Global Mirror or Global Copy targets, are also not affected.

Recommended Action

Mitigation:

Disable zHyperLink write at a host system level or on the DS8000, until a fix is available and applied.

zHyperLink write may be disabled at the host by:

DB2 link: https://www.ibm.com/docs/en/db2-for-zos/13.0.0?topic=panel-db2-zhyperlinks-scope-field-zhyperlink-subsystem-parameter
MQ link: https://www.ibm.com/docs/en/ibm-mq/9.4.x?topic=zos-faster-log-throughput-zhyperlink
zOS/zOS DFSMS: https://www.ibm.com/docs/en/zos/2.5.0?topic=performance-zhyperlink-io

zHyperLink write may be disabled at the DS8000 by:

Use this link to disable/enable zHyperLink write on the DS8000 using the DS8000 Storage Manager: 
Getting Started with IBM zHyperLink for z/OS Section 3.1.5

zHyperLink reads are not affected by this mitigation, and may remain active.

Contact IBM support if assistance is needed to disable zHyperLink write.

Fix:

R10.1 SP1.1 - 10.11.34.0
R9.4 The Fix is Planned to release in 1Q 2026.
After the fix is applied, zHyperLink write may be re-enabled.

Reference ID

374034

Date first published

28 January 2026

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Document Information

Modified date:
26 February 2026

UID

ibm17258228

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