Manual Path Switching - Hitachi XP P9500 User Manual

Series, or Hitachi SMS is being used, all the paths are owner paths.
Therefore, if an owner path recovers from an error and HDLM automatically
places the recovered path online, the path in use will not be switched to the
recovered owner path.
When intermittent errors
failback function, the path status might frequently alternate between the
online and offline statuses. In such a case, because the performance of I/Os
will most likely decrease, if there are particular paths in which intermittent
errors might be occurring, we recommend that you set up intermittent error
monitoring so you can detect these paths, and then remove them from those
subject to automatic failbacks.
You can specify the automatic failback function or intermittent error
monitoring by the dlnkmgr command's set operation. For details on the set
operation, see
#
An intermittent error means an error that occurs irregularly because of,
for example, 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
page
Paths Offline) on page
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 the Thunder 9500V Series, or Hitachi AMS/WMS series is being used,
HDLM selects the switching destination path from owner paths and then from
non-owner paths. When the Lightning 9900 Series, Lightning 9900V Series,
Hitachi USP, Universal Storage Platform V/VM, Virtual Storage Platform,
Hitachi AMS2000 Series, or Hitachi SMS is being used, all paths that access
the same LU are candidates for the switching destination path.
Paths are switched in units of physical paths. Therefore, if an error occurs in a
path, all the 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
2-18
#
occur on paths and you are using the automatic
set (Sets Up the Operating Environment) on page
6-11. For details on the offline operation, see
6-6.
online (Places Paths Online) on page
HDLM Functions
Hitachi Dynamic Link Manager User Guide (for Solaris(R))
online (Places Paths Online) on
offline (Places
6-11. After
6-16.