Hitachi Dynamic Link Manager Software Users Guide for AIX (6.6) (T5208-96010, April 2011)

2. HDLM Functions

2.8 Monitoring intermittent errors (functionality when automatic

failback is used)

An intermittent error refers to an error that occurs irregularly because of something

like a loose cable. In such a case, I/O performance might decrease while an automatic

failback is being performed to repair an intermittent error. This is because the

automatic failback operation is being performed repeatedly (because the intermittent

error keeps occurring). To prevent this from happening, HDLM can automatically

remove the path where an intermittent error is occurring from the paths that are subject

to automatic failbacks. This process is called intermittent error monitoring.

We recommend that you use intermittent error monitoring along with the automatic

failback function.

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 chooses to place the path back online. Failbacks are

not performed for such paths. This status is referred to as the not subject to auto

failback status.

2.8.1 Checking intermittent errors

You can check the paths in which intermittent errors have occurred by viewing the

execution results of the HDLM command's

view operation.

For details on the

view operation, see 6.7 view (Displays Information).

2.8.2 Setting up intermittent error monitoring

When you enable the intermittent error monitoring function, specify the following

monitoring conditions: the error monitoring interval, and the number of times that the

error needs to occur. If an error occurs on a particular path the specified number of

times within the specified error-monitoring interval, then an intermittent error will

occur on the path. For example, if you specify 30 for the error monitoring interval and

3 for the number of times that the error needs 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.

Intermittent error monitoring can be used only when automatic failback has already

been enabled. The values that can be specified for intermittent error monitoring depend

on the values specified for automatic failbacks. For details on how to specify the

settings, see 6.6 set (Sets Up the Operating Environment).