I would like to understand how a management module can disappear without it being deleted?
Only one management module disappeared.
We have lost alerts and lots of work to recreate this.
Review of Enterprise Manager logs, including APMAudit.log may be able to determine cause but the aim of this article is to highlight how to recover from this.
Release : 10.7.0
Component : APM Agents
While the live management modules are kept in the /config/modules folder of the Enterprise Manager, a backup copy is kept in /config/modules-backup In the backup, the files have the .backup extension.
Assuming your missing management module is present in the backup folder, you can use the backup copy, removing the .backup extension, so the file ends with the normal .jar extension.
As long as this management module does not have the same name as any other management module, you can put it into the /deploy folder of the Enterprise Manager and it will be loaded without needing to restart the Enterprise Manager.
This highlights a general recommendation for backup of Enterprise Manager configuration, at least the /config/modules folder.
Documented mention of the backup folder which suggests using a backup copy may sometimes be necessary.