Potential DS8700/DS8800 Loss of Access and Job Abends on Release 6.2 due to repeating device recovery with the PTFs for OA34661 installed on z/OS releases 1.11 through 1.12. Also base z/OS 1.13 clients are exposed.

Flash (Alert)


Abstract

When running a zHPF chain containing the rare new combination of both update and format writes (on DS8000 bundles 76.20.x.y or 86.20.x.y), a DS8700/DS8800 host adapter microcode error will occur. If the chain is redriven, repeating microcode errors will occur. These repeating errors lead to fenced host adapter cards and potential loss of access. DS8100s and DS8300s are not exposed to this issue. Users with DS8700 or DS8800 machines below Release 6.2 are not exposed. Users without the OA34661 PTFs on z/OS releases 1.11 through 1.12 are not exposed.

Content

With z/OS OA34661 support and Release 6.2 DS8700/DS8800 microcode, System z High Performance FICON (zHPF) supports additional workloads using QSAM, BPAM, and BSAM access methods as well as provide improvements for access methods and middle ware that use the Media Manager as an IO driver (examples include PDSE, VSAM, VSAM/RLS, zFS, HFS, DB2, and IMS). The Release 6.2 microcode also provides special improvements for DB2 list prefetch processing. These changes expand the type of applications that can now use zHPF, including applications performing format writes. The zHPF support must be enabled in both the host system and DS8000 in order for the new functions to be allowed. Most access methods exploiting the new zHPF support and those who call Media Manager do not use format write/update write intermixed in the same channel program. However, Media Manager does have the ability to generate zHPF channel programs with format write/update write intermixes, and the new support for format writes allows it to be done using zHPF. The HFS access method currently has the code to request that Media Manager intermix format write/update write in a single channel program. When such an intermix is processed in the control unit using a zHPF channel program, repeating panics will occur leading to fenced host adapter cards and potentially a loss of access issue.

Mitigation
Avoiding the installation of or removing the PTFs for OA34661 on 1.11 - 1.12 or base z/OS 1.13 or not installing DS8000 Release 6.2 will avoid the issue. Users who do not use the HFS file system may not be exposed. Otherwise, the zHPF function must be disabled when the new functions are supported by both the z/OS Host and DS8000 storage system, until the resolution mentioned below is available. zHPF may be disabled in one of two ways: either by turning off the DS8000 LIC feature code or via the SETIOS ZHPF=NO command.

Resolution
Media Manager has provided a fix in the following PTFs:

PTF No. Rel Id  Status  PTF No. Rel Id  Status  PTF No. Rel Id  Status
UA63528 HDZ1B10 BUILT   UA63529 HDZ1C10 BUILT   UA63530 HDZ1D10 BUILT

When the PTF code detects both update and format writes for the same channel program and determines that the storage system does not have support for such zHPF intermix, a FICON channel program will be created, rather than using zHPF.


Cross reference information
Segment Product Component Platform Version Edition
Disk Storage Systems System Storage DS8700 Not Applicable z/OS 6.2 N/A

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Document information


More support for:

System Storage DS8800

Version:

6.2

Operating system(s):

z/OS

Software edition:

N/A

Reference #:

S1003953

Modified date:

2012-01-14

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