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 205
Auto failback
Specify whether or not the auto failback function is to be used.
To use the function, select ON; otherwise, select OFF.
When ON is selected, you can specify the interval (in minutes) at which the path status
is checked. Specify a value from 1 to 1440 minutes. The default, which is also the
recommended value, is 1. Set the value depending on system operations.
If the intermittent error monitoring is ON and the number of times that an error is to
occur is set to a value of 2 or more, the following condition must be satisfied:
error-monitoring-interval >= checking-interval-for-automatic-failback x number-of-
times-error-is-to-occur-during-intermittent-error-monitoring
If this condition is not satisfied, the KAPL02064-W message is output and an error occurs.
In such a case, change any of the following settings; the checking interval for automatic
failback, intermittent error monitoring interval, or the number of times that an error is
to occur.
When you set the number of times that an error is to occur to 1, the above condition
does not need to be satisfied.
If you change the checking interval, the new interval takes effect immediately. If you
shorten the checking interval and a status check is already overdue on the basis of the
new checking interval (since the last path status check was completed), path status
checking begins immediately.
Once a checking interval is set, it remains in effect even if the auto failback function is
subsequently changed from OFF to ON. In such a case, path status checking begins when
the specified checking interval elapses since the auto failback function setting was
changed to ON.
Table 6.11 shows the advantage and disadvantages of setting the auto failback function
to ON.
Table 6.11 Advantage and Disadvantages of Setting the Auto Failback Function to ON
Advantage Disadvantage
Paths where errors have occurred are activated
automatically.
 A path that has been shut down intentionally
(Offline(E)) by the user (such as for maintenance
purposes) may be activated automatically.
 If there is a recurring failure in a storage system
or on a path, I/O performance may become
degraded because the path's status changes
repeatedly between shutdown and active.
#
#
To prevent an intermittent error from reducing I/O performance, we recommend that
you also enable intermittent error monitoring when enabling automatic failback.
Intermittent error monitoring can only be specified when automatic failback is enabled.
For details about the relations of the settings for automatic failback and intermittent
error monitoring, see
Table 6.12.
Intermittent Error Monitor
Intermittent Error Monitor can only be specified when Auto failback is set to ON.