Notification
Risk classification
HIPER (High Impact and/or Pervasive)
Risk categories
Severe Performance Impact
Affected Domain
DS8900F systems running 89.40.83.0 or 89.40.89.0 Bundles
Abstract
DS8900F systems running 89.40.83.0 or 89.40.89.0, and using zHyperLink write, combined with FICON (zHPF) read workloads, may experience performance impacts.
Description
While a zHyperLink (zHL) write chain is being processed, aggressive zHPF read operations are allowed to interrupt the zHL write chain, to read the same track that is in the process of being written. Once interrupted, zHL access is not re-obtained, and the interrupted write activity is then performed using zHPF, reducing the synchronous write success rates.
Recommended Action
Mitigation:
Contact IBM support to have pokeable cdHLDelayTrackRecallTime set on affected DS8900F systems.
Fix:
Install R9.4 GA3 - 89.40.93.0 or newer.
Reference ID
365231
Date first published
23 September 2024
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Document Information
Modified date:
23 September 2024
UID
ibm17168984