HP XP Racks - Manual (Page 39)

#1
This storage system applies when the dynamic I/O path control function is
disabled.
#2
An intermittent error means an error that occurs irregularly because of
some reason such as a loose cable connection.
Manual path switching
You can switch the status of a path by manually placing the path online or
offline. Manually switching a path is useful, for example, when system
maintenance needs to be done.
You can manually place a path online or offline by doing the following:
• Execute the dlnkmgr command's online or offline operation.
For details on the online operation, see
online (Places Paths Online) on
page 6-11 . For details on the offline operation, see offline (Places
Paths Offline) on page 6-6 .
However, if there is only one online path for a particular LU, that path cannot
be manually switched offline. Also, a path with an error that has not been
recovered from yet cannot be switched online.
HDLM uses the same algorithms to select the path that will be used next,
regardless of whether automatic or manual path switching is used.
When using the Thunder 9500V series, or Hitachi AMS/WMS series HDLM
selects the switching destination path from owner paths and then from non-
owner paths. When the Lightning 9900V series, Hitachi USP series, Universal
Storage Platform V/VM series, Virtual Storage Platform series, Hitachi
AMS2000 series
# , Hitachi SMS series, or HUS100 series # is being used, all
paths that access the same LU are candidates for the switching destination
path. All other paths that run through the same physical path are switched.
Executing the online operation places the offline path online. For details on
the online operation, see online (Places Paths Online) on page 6-11 . After
the path status is changed to online (by executing the online operation),
HDLM selects the path to use in the same way as for automatic path
switching. When using the Thunder 9500V series, or Hitachi AMS/WMS series
HDLM selects the path to use from online owner paths, and then from online
non-owner paths. When the Lightning 9900V series, Hitachi USP series,
Universal Storage Platform V/VM series, Virtual Storage Platform series,
Hitachi AMS2000 series
# , Hitachi SMS series, or HUS100 series # is being
used, since all the paths are owner paths, the path to use is not switched
even if you change the path status to online by using the online operation.
#
This storage system applies when the dynamic I/O path control function is
disabled.
HDLM Functions
2-19
Hitachi Dynamic Link Manager User Guide for AIX®