HiCommand Dynamic Link Manager User's Guide (for Windows(R))

2.7.3 Path status transition

This subsection explains the online and offline path statuses described in 2.7 Failover and failback using path switching. There are four types of online status, and three types of offline status. A description of each type of status is provided below. In the descriptions, an offline operation refers to performing an offline operation by using the Path Management window in HDLM GUI, or by executing the dlnkmgr command's offline operation. For details on the offline operation, see 7.4 offline (Places a path or paths offline).

Organization of this subsection

(1) The online path status

(2) The offline path status

(3) Status transitions of a path

(1) The online path status

The online path statuses are as follows:

Online
I/O can be issued normally.

Online(P)
A state in which offline processing, for a path in the Online status, is in the waiting-to-execute status.
This status occurs in a cluster configuration only.
The Online(P) status indicates that the user performed an offline operation on an Online path that is connected to an LU for which reserve processing was being performed. I/O operations can be issued normally until such reserve processing finishes. After the reserve processing finishes, the offline operation is performed and the path status becomes Offline(C).
The (P) indicates the pending attribute, which indicates that the offline operation on the path has a waiting-to-execute status.

Online(E)
An error has occurred on the path and, among the paths that access the same LU, none of those are in the Online status.
If none of the paths accessing a single LU are in the Online status, one of the paths is changed to the Online(E) status. This ensures that the LU can be accessed, by making sure that all paths are not offline.
The (E) indicates the error attribute, which indicates that an error occurred in the path.

Online(EP)
The status of an Offline(P) path changes to Online(EP) when the path goes through the following process during reserve processing in a cluster configuration:

When two paths are connected to an LU, and then the user performs an offline operation on the Offline(E) path to change it to Offline(P).
The other path is Online(E).

When one of the paths is Offline(P), the other path is Online(E), and HDLM detects an error in the Online(E) path, then the path statuses change as follows:
The Online(E) path changes to Offline(E).
The Offline(P) path changes to Online(EP).

If the reserve processing finishes after the path has changed from Online(EP) to Offline(P), the offline operation ends successfully and the path changes to Offline(C).
If the reserve processing finishes while the path is Online(EP), the offline operation fails and the path changes to Online(E).

(2) The offline path status

The offline path statuses are as follows:

Offline(C)
The path is offline because an offline operation was performed.
The (C) indicates the command attribute, which indicates that the path was placed offline by using the GUI or a command.

Offline(E)
The status in which I/O cannot be performed because an error occurred in the path.
The (E) indicates the error attribute, which indicates that an error occurred in the path.

Offline(P)
This status occurs in a cluster configuration only.
The Offline(P) status indicates that the user performed an offline operation on an Offline(E) path that was connected to an LU for which reserve processing was being performed. After the reserve processing finishes, the offline operation is performed and the path status becomes Offline(C).
The (P) indicates the pending attribute, which indicates that the offline operation on the path has a waiting-to-execute status.

(3) Status transitions of a path

Figure 2-11 Path status transitions shows the status transitions of a path.

Figure 2-11 Path status transitions

Legend:

Online operation: Online operation performed in the Path Management window or by executing the dlnkmgr command's online operation.

Offline operation: Offline operation performed in the Path Management window or by executing the dlnkmgr command's offline operation.

#1

During reservation processing for an LU, the Online status is temporarily changed to Online(P). When the reservation processing finishes, the Online(P) status is changed to Offline(C).

#2

When the following conditions are satisfied, the connected Offline(C) paths are automatically placed online:

All the online paths are Online(E) and SCSI devices connected to the Online(E) paths have been deleted.

SCSI devices are connected and all Offline(E) paths are subject to automatic failback.

SCSI devices are connected to the Offline(C) paths.

#3

When a path is added dynamically, initially the path status is Offline(C). The path status will then automatically change to Online. For details on the path dynamic addition functionality, see 4.6.1 Setting up an added LU and path as an HDLM management-target.

#4

When the following conditions are satisfied, a path that has been determined to have an intermittent error also becomes subject to automatic failback:

All the paths connected to an LU are Online(E), Offline(E), or Offline(C).

All the paths connected to an LU have been determined to have an intermittent error.

The processing of continuous I/O operations issued to an LU is successful.

#5

During reservation processing for an LU, the Offline(E) status is temporarily changed to Offline(P). When the reservation processing finishes, the Offline(P) status is changed to Offline(C).

#6

When the following conditions are satisfied, the connected Offline(E) paths are automatically placed online:

All the online paths are Online(E) and SCSI devices connected to the Online(E) paths have been deleted.

The Offline(E) paths are assumed to have had an intermittent error, and are excluded from automatic failback.

The SCSI devices are connected to the Offline(E) paths.

The last available online path for each LU cannot be placed offline by using the Path Management window or by executing the offline operation. This ensures access to the LU. For details on the offline operation, see 7.4 offline (Places a path or paths offline).

If an error occurs in the last available online path for each LU, the status of the path is changed to Online(E).

If you are using automatic failback, when the path recovers from an error, HDLM automatically places the path online. However, there are the following exceptions:

When you are using intermittent error monitoring, the path in which the intermittent error occurred is not automatically placed online when the path recovers from the error. In such a case, place the path online manually. If the only online path is Online(E) when the path is recovered from the error, the path might be placed online automatically. For details, see Figure 2-13 Action when an intermittent error does not occur in the path.

There is a case in which the path is automatically placed online even if you are not using the automatic failback function. If you remove the hardware that supports the Windows plug and play function, HDLM places the path offline. Then, HDLM automatically places the path back online when the hardware is re-installed. However, this applies only when there is no other cause for the path being placed offline. Since HDLM automatically places the path online without using the automatic failback function, you do not need to place the path online manually.

When you use the LU dynamic deletion functionality, the path whose status is Online(E) is deleted. Therefore, the path whose status is Online(E) is not displayed in the Path Management window. Also, the view operation does not display the path whose status is Online(E).

Note

If there is a path failure immediately after a path is made offline by using an HDLM command or HDLM GUI, Offline(C) might change to Offline(E). If an offline operation was performed, wait for a fixed period of time (about 2 minute), check the path status by using an HDLM command or HDLM GUI, and make sure that the status has changed to Offline(C). If it is Offline(E), retry the offline operation.

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