Potential DS8100/DS8300/DS8700 FICON Host Adapter Loss of Access due to unavailable adapters during certain zHigh Performance FICON (zHPF) workloads.

Flash (Alert)


Abstract

Customers running zHPF enabled on DS8100/DS8300 with Release 4.3 code bundle levels 64.30.78.0 and higher or DS8700 with Release 5.0 code bundle level 75.0.x.y may see global CRC checks or repeating host adapter error recovery leading to unavailable host adapter cards and potential loss of access. DS8700s on Release 5.1 bundle levels 75.1.x.y are not exposed. DS8800s are not exposed.

Content

zHPF Read Multi-Track chains on exposed DS8000 storage control units/code levels can cause global CRC checks or repeating host adapter errors under certain conditions. These conditions relate to track format and data transfer sizes which result an incorrect setup of DMA transfers for the read. The problem will only occur with CKD records with a data lengths of less than 128 bytes and DCW data lengths larger than 16K bytes. This problem can be exposed by the application of APAR OA34661 on z/OS V1 R11 and V1 R12; and is also exposed at the base level of z/OS V1 R13. APAR OA34661 enhanced the construction of zHPF channel programs making it possible to transfer larger amounts of data in a single channel program. In certain instances this capability allows certain IO requests for small CKD records to exceed the 16K byte threshold that exposes this microcode defect.
Mitigation

  • DS8700s running zHPF on Release 5.0 should be moved to Release 5.1 or higher (release 6.2 bundle 76.20.82.0 is recommended). HIPER APAR OA38777 will also be available by the end of February to ensure that Media Manager zHPF channel programs do not exceed 16K byte data transfer for Multi-Track Read IO for records with data lengths less than 128 bytes as a bypass for the defect.
  • DS8100/DS8300s running zHPF should not be moved to a Release 4.3 bundle without applying the HIPER APAR just mentioned, unless zHPF is disabled until the HIPER APAR is applied. DS8100s/DS8300s already on release 4.3 code (64.3x.xx.0) should also apply this HIPER APAR when it is available. DS8100s / DS8300s with Release 4.3 code, and currently running with zHPF, planning to update software service levels prior to the HIPER APAR availability should disable zHPF until the HIPER APAR is applied.
If you have additional questions, please contact the DS8000 Quality Warranty Team at ds8kqwt@us.ibm.com.

Resolution
DS8700 customers should move to Release 6.2 ( bundle 76.20.90.0 or higher is recommended ).
DS8100 / DS8300 customers should move to bundle 64.36.44.0 or higher.

Cross reference information
Segment Product Component Platform Version Edition
Disk Storage Systems TotalStorage DS8300 Not Applicable z/OS Version Independent N/A
Disk Storage Systems TotalStorage DS8100 Not Applicable z/OS Version Independent N/A

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Document information


More support for:

System Storage DS8700

Version:

5.1.5

Operating system(s):

z/OS

Software edition:

N/A

Reference #:

S1004012

Modified date:

2014-01-09

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