Troubleshooting
Problem
SAN disk issue impacting IBM i - missing path errors
Symptom
Missing path errors
Cause
external to IBM I
Environment
SAN disk environments
Diagnosing The Problem
The missing disk path issue is a common problem with SAN customers. This error can occur when the presentation of the SAN provided disks changes. This does not necessarily mean there is a problem, just that IBM i knows about more paths for a disk LUN than what is currently seen. This can be from either a planned change to the SAN zoning or external storage configuration, or it could actually represent a loss of redundancy in the Storage Area Network.
The first step is to determine how many paths should be seen by IBM i.
If IBM i sees fewer paths than what the SAN is supposed to be presenting, then there is a problem that needs to be investigated. Start by contacting the SAN and zoning administrator to look for errors or unexpected changes to the network. While that is taking place also please ensure that the system experiencing the issue is at CURRENT CUMULATIVE MAINTENANCE, Group PTFs, Hyper PTFs and Server Firmware. If the PTF groups are up to date and the SAN administrator has not resolved the issue, QMGTOOLS can be used to gather a System Snap Shot Collection (see document https://www.ibm.com/support/pages/node/706461) - be sure to specify OUTPUT(*IFS) LICLOGS(Y) QHST(Y/Y).
However, if IBM i sees more paths that what should be presented by the SAN, this may be due to an accidental misconfiguration that was later corrected, or it could be intentional and expected. For example, if the SAN configuration was specifically changed to reduce the number of paths from 4 to 2, then the missing path errors are normal and expected. Also when FlashCopy is used to replicate LUNs to another partition (such as for performing backups), IBM i still knows about the paths to the source LUNs, and it now has new paths to the replicated LUNs. Missing path messages will be issued for all of the original source LUNs. These errors are expected and can be resolved by resetting the number of paths that IBM i is expecting by using the following Advanced Analysis command -
- Start system service tools using the STRSST command, and sign in. Select option 1 to Start a Service Tool, option 4 - Display/Alter/Dump, option 1 - Display/Alter storage, option 2 - LIC data, option 14 Advanced analysis. Find MULTIPATHRESETTER in the list and select with option 1 and press enter. On the options screen type -RESETMP -ALL or instead of -ALL, you can use -DISK and specify the resource name(s), such as DMP001 (you can press F4 to see help). After pressing ENTER, read the screen carefully for instructions on how to confirm the reset operation.
See the links below related to multipath environments which may be useful in helping you understand how this environment works.
Related Information
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Document Information
Modified date:
07 June 2022
UID
nas8N1022395