Linux on IBM Z - dasd devices fail to attach, accompanied with messages "Setting the DASD online with discipline DIAG failed with rc=-95"

Solution Verified - Updated -


DASD storage on IBM Z series running Red Hat Enterprise Linux with use_diag=1 setting fails with boot up messages like:

0.0.0300: A 64-bit DIAG call failed
dasd: 0.0.0300 Setting the DASD online with discipline DIAG failed with rc=-95


  • Red Hat Enterprise Linux 7 on IBM Z (mainframe)
  • kernel 3.10.0-1160.el7.s390x -- detected on this kernel version, but the issue exists on versions pre-dating kernel-3.10.0-1160.10.1.el7
  • DASD storage and driver presence
  • use_diag flag is set (use_diag=1)

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