HiCommand Dynamic Link Manager (HDLM) for Windows Systems User's Guide (HIT5201-96001, January 2008)

HiCommand
®
Dynamic Link Manager (HDLM) for Windows
®
Systems User’s Guide 29
2.7.1.2 Automatic Failback
After a path recovers from an error, HDLM can automatically place the recovered path
online. This functionality is called automatic failback.
When using this function, HDLM monitors error recovery on a regular basis.
When using the TagmaStore AMS/WMS series, Thunder 9500V Series, or Thunder 9200, HDLM
selects the path to use from online owner paths, and then from online non-owner paths.
Therefore, if an owner path recovers from an error and HDLM automatically places the
recovered path online while any non-owner path is in use, the path to use is switched to the
owner path.
When the Lightning 9900 Series, Lightning 9900V Series, TagmaStore USP, or Universal
Storage Platform V 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
to use is not switched.
An intermittent error is an error that occurs irregularly because of some reason such as a
loose cable connection. When intermittent errors occur in paths, the path status may
frequently alternate between the online and offline status if you are using automatic
failback, so the I/O performance might deteriorate. In such a case, if there is a path in
which an intermittent error might be occurring, we recommend that you set up intermittent
error monitoring to remove that path from those subject to automatic failback.
You can specify the automatic failback function or intermittent error in the Options window
of the HDLM GUI or by the dlnkmgr command's set operation. For details on the operation
in the Options window, see sections
4.2.8 and 6.3. For details on the set operation, see
section
7.6.