Detecting Errors By Using Path Health Checking; Error Management - Hitachi XP P9500 User Manual

The number of errors and the time passed since error monitoring had
started are both reset to 0, and then monitoring restarts from the time
the HDLM manager starts.

Detecting errors by using path health checking

HDLM can check the status of paths for which I/O operations are not being
performed at regular intervals. This function is called path health checking.
Without path health checking, an error is not detected unless I/O is
performed because the system only checks the path status when I/O is
performed. With path health checking, however, the system checks the status
of online paths at regular intervals regardless of whether I/O is performed. If
an error is detected in a path, path health checking functionality switches the
status of that path to Offline(E) or Online(E), so you can use the dlnkmgr
command's view operation to check the path error.
For example, in a normal state, I/O operations are not performed on the
paths coming from the standby host in the cluster configuration or on non-
owner paths (that is, some of the paths that access a Thunder 9500V series
and Hitachi AMS/WMS series storage system). Because of this, for the
standby host or for a host connected to non-owner paths, we recommend
that you use path health checking to detect errors. This enables the system
to use the most up-to-date path-status information when selecting the next
path to use.
You can configure path health checking by executing the dlnkmgr command's
set operation. For details on the set operation, see
Operating Environment) on page

Error management

For troubleshooting purposes, HDLM collects information and stores it into log
files. The error information to be collected can be filtered out by error level,
and then stored into the log files.
Figure 2-13 Flow of Data When Collecting Error Information on page 2-29
shows the flow of data when collecting error information.
2-28
HDLM Functions
Hitachi Dynamic Link Manager User Guide (for AIX(R))
set (Sets Up the
6-16.