While restarting the host, HDLM may detect a new path. The HDLM device to be allocated depends on whether the SCSI device for the detected path is already registered or a new SCSI device is registered. This section describes a situation where the HDLM device that is to be allocated to the newly detected path is already registered and a situation where a new HDLM device is created.
If the SCSI device of the new path that HDLM detected is already registered, the HDLM device mapped with the path already registered is allocated. For example, if the path between the host and an LU of the storage system already exists and a new path is added, the HDLM device that already exists is allocated to the path.
If the SCSI device of the new path that HDLM detected is not yet registered, a new HDLM device is allocated to the path. For example, if you define a new path from the host to an LU of the storage system, a new HDLM device is allocated to the path. The lowest available alphabetical letter is allocated as the logical device file name of the HDLM device.
Examples of the logical device file names for HDLM devices when a new HDLM device is allocated are shown in the following table.
Allocation before restarting the host |
Allocation after restarting the host |
|---|---|
none |
/dev/sddlmaa# |
|
/dev/sddlmaa |
/dev/sddlmaa /dev/sddlmab# |
|
/dev/sddlmaa /dev/sddlmab |
/dev/sddlmaa /dev/sddlmab /dev/sddlmac# |
|
/dev/sddlmaa /dev/sddlmac |
/dev/sddlmaa /dev/sddlmab# /dev/sddlmac |
|
/dev/sddlmab /dev/sddlmac |
/dev/sddlmaa# /dev/sddlmab /dev/sddlmac |
|
/dev/sddlmaa : /dev/sddlmpp |
/dev/sddlmaa : /dev/sddlmpp /dev/sddlmaaa# |
|
/dev/sddlmaa : /dev/sddlmaap |
/dev/sddlmaa : /dev/sddlmaap /dev/sddlmbaa# |
If the error message KAPL10357-E is displayed, HDLM does not add an HDLM device even though a new LU was recognized. In this case, you must execute the HDLM-configuration definition utility (dlmcfgmgr -u) to delete the HDLM device(s) not in use (or, represented with a hyphen (-)) to release the available name(s) to create an HDLM device file for the new LU.
Even if you add a path to an HDLM device that is not managed by HDLM and restart the host, the HDLM device will not be managed by HDLM.
An AutoPATH_ID is allocated sequentially as the HDLM recognizes a SCSI device during start up of the host. Therefore, an AutoPATH_ID for the same path may change whenever the host starts.
If a different LU is allocated to the same path name, a new HDLM device will be allocated to the newly allocated LU after restarting the host restarts. In such case, the previous HDLM device is unregistered automatically.