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Troubleshooting
Problem
While using the 'chdev' command to switch from SCSI-3 to SCSI-2 reservation methodology or remove the SCSI-3 reservation methodology:
# chdev -l hdisk# -a reserve_policy=single_path
may result in the message when the device is in 'Defined' state:
Method error (/usr/lib/methods/chgdisk):
0514-047 Cannot access a device.
0514-047 Cannot access a device.
This document explains the error and how to troubleshoot the issue.
Symptom
When running a 'chdev' command on a hdisk device that is in 'Defined' state, we'll generate the message below:
# rmdev -Rl hdisk#
hdisk# Defined
# chdev -l hdisk# -a reserve_policy=no_reserve
Method error (/usr/lib/methods/chgdisk): 0514-047 Cannot access a device.or
# rmdev -Rl hdisk#
hdisk# Defined
# chdev -l hdisk# -a reserve_policy=single_path
Method error (/usr/lib/methods/chgdisk): 0514-047 Cannot access a device.Cause
The "SCSI reservation" option helps manage the access to a shared SCSI device, such as a disk or tape drive.
When a SCSI-3 persistent reservation is established on a device, multiple initiators (nodes) gain permission to use it, simultaneously preventing other initiators from accessing it.
To transition from SCSI-3 to SCSI-2 reservation or remove the SCSI-3 reservation methodology, choose from one of the following scenarios:
Scenario 1: Lock the device to a single initiator - this can be achieved by configuring the 'reserve_policy' to 'single_path'.
Scenario 2: Enable the disk to be available for all initiators by configuring the 'reserve_policy' to 'no_reserve'
In both cases, if device is placed in 'Defined' state, it will face difficulties transitioning to 'no_reserve' or 'single_path'.
Environment
AIX 7.1, 7.2, 7.3
Resolving The Problem
Choose the option for your scenario.
Option 1. Active device change - Changes the characteristics of the device while allowing the device to remain in the 'Available' state
Use the flag '-U' with 'chdev' to apply the change while the device remains in 'Available' state.
# chdev -l hdisk# -a reserve_policy=no_reserve -URun the following command to determine whether the device supports dynamic change of an attribute value:
# lsattr -El hdisk# -a reserve_policy
reserve_policy PR_exclusive Reserve Policy True+The 'True+' label against an attribute indicate the flag '-U' can be used with 'chdev' and no reboot is needed to apply the change in the kernel.
Option 2. Delay device change - Changes the characteristics of the device configuration but does not change the active device
Use the flag '-P' with 'chdev' then reboot.
# chdev -l hdisk# -a reserve_policy=no_reserve -P
# shutdown -rNot all devices support changes of an attribute while device is in 'Available' state.
Run the following command to determine whether the device supports dynamic change of an attribute value:
# lsattr -El hdisk# -a reserve_policy
reserve_policy PR_exclusive Reserve Policy TrueThe 'True' label against an attribute indicate the flag '-P' should be used with 'chdev', and reboot is needed to make the change effective in the kernel.
For further assistance we recommend you open an IBM Support case using the following instructions:
1. Document (or collect screen captures of) all symptoms, errors, and messages related to your issue.
2. Capture any logs or data relevant to the situation.
3. Contact IBM to open a case:
-For electronic support, visit the IBM Support Community Page to View and Open Cases:
https://www.ibm.com/mysupport
-If you require telephone support, see the web page:
https://www.ibm.com/planetwide/
4. Provide a clear, concise description of the issue.
- For guidance, provide these answers in your description:
- What is your preferred communication method?
- List any error messages (provide full output)
- Describe the unexpected behavior
- List all applications possibly associated with the problem
- List all steps to reproduce the problem if possible
- When did the problem begin?
- Were any changes applied to the product, or system, which seemed to introduce this problem?
5. If the system is accessible, collect a system snap, and upload all of the details and data for your case.
- For guidance, select the Mustgather page for your product:
Related Information
Document Location
Worldwide
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Document Information
More support for:
AIX 7.2 Enterprise Edition
Component:
IO Device Drivers
Software version:
All Versions
Document number:
7015875
Modified date:
29 August 2023
UID
ibm17015875
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