Avamar: Hyper-V Backups Generating UI Event Warning 30923

Summary: Hyper‑V backups complete, but the Avamar UI logs warning 30923 for a “Naked Ad Hoc” (NAH) activity with a non‑unique session ID; caused by scripts or backup restore jobs reusing a session ID. ...

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Symptoms

Hyper-V backups complete successfully, but Event warning 30923 messages are displayed in the Avamar Administrator console:

MCS Event Detail
 

2022/06/14-20:01:11 CDT 30000 INFO ave01 Activity completed successfully.
2022/06/14-20:01:11 CDT 30000 INFO ave01 Activity completed successfully.
2022/06/14-20:01:11 CDT 30923 WARN ave01 Client NAH activity with non-unique sessionid for clientname HyperV-av and pidnumber 3001

Cause

A script may be running between the client and the Avamar server, causing the client to initiate more than one concurrent NAH activity. Because the Management Console Database (MCDB) cannot guarantee generation of a unique session ID under concurrent activity, duplicate session IDs may occur. The term NAH refers to Naked Ad Hoc backups, which are manually initiated backups or backups triggered through custom scripts.

Resolution

These MCS warning messages can be ignored.

To suppress the warning messages from being displayed in the Avamar Administrator UI: 

  • Add the following flag to the avtar.cmd file. 
    --x03=512
  • This file can be found in the shared var directory on each cluster node. 
    C:\ClusterStorage\Volume10\Ava_hv\var

C:\Program Files\avs\var
  • If avtar.cmd file does not exist, manually create it using Notepad.

Additional Information

During an incremental backup, a single NAH activity is initiated to restore the inode2hash table from the server.

  • All NAH activity during this process uses the same session ID.

When multiple CLI commands or scripts attempt both backup and restore operations on the same inode2hash table while sharing the same session ID, the activity conflicts.

  • This triggers MCS to generate the warning:


NAH activity with non‑unique session id.

To prevent this warning, use the following avtar flag. 

--x03=512
  • This flag suppresses the session information for backup or restore operations, avoiding session ID conflicts.

Affected Products

Avamar Plug-in for Hyper-V VSS, Avamar Server
Article Properties
Article Number: 000207143
Article Type: Solution
Last Modified: 27 Feb 2026
Version:  3
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