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

36 Chapter 2 HDLM Functions
2.8 Monitoring Intermittent Errors
An intermittent error means an error that occurs irregularly because of some reason such as
a loose cable connection. I/O performance might decrease when an intermittent error
occurs while automatic failback is used, because automatic failback is performed
repeatedly. To prevent this phenomenon, HDLM can automatically remove the path where
an intermittent error is occurring from those paths subject to automatic failback. This
process is called intermittent error monitoring.
We recommend that intermittent error monitoring be used along with automatic failback.
With intermittent error monitoring, a path in which an error occurs a specified number of
times within a specified interval is determined to have an intermittent error. The path
where an intermittent error occurs has an error status until the user places the path online.
Failback is not performed for the path. This status is called not subject to auto failback.
2.8.1 Checking Intermittent Errors
You can check the path in which an intermittent error occurs by using the execution result
of the HDLM command's view operation or the HDLM GUI Path List view.
For details on the view operation, see section
7.7. For details on how to use the Path List
view of the HDLM GUI and the window components, see sections
4.2.3.2 and 6.2.4.
2.8.2 Setting up Intermittent Error Monitoring
When you use the intermittent error functionality, you can enable or disable the
functionality. If you enable the functionality, specify the monitoring conditions: the error
monitoring interval, and the number of times that the error is to occur. If an error occurs in
a path the specified number of times within the specified error monitoring interval, the
system determines that the path has an intermittent error. For example, if you specify 30
for the error monitoring interval and 3 for the number of times that the error is to occur,
the path is determined to have an intermittent error if an error occurs 3 or more times in 30
minutes.
You can set up intermittent error monitoring by executing the dlnkmgr command's set
operation or using the Options window of the HDLM GUI.
Intermittent error monitoring can be used only when automatic failback is enabled. The
setting value depends on the setting value for automatic failback. For details on how to set
up the setting values, see sections
7.6 and 6.3.
2.8.3 Actions for Intermittent Error Monitoring
Intermittent error monitoring is performed for each path,. and it starts when a path is
recovered from an error by using automatic failback.
This subsection describes the following actions for intermittent error monitoring: