After upgrade from 10.3 to 10.5 the MOM log is full of WARNing messages "Metric key id 0xnnnnnnnn illegally used by two metrics ...." which are repeated every 15 seconds e.g.
[WARN] [Smartstor/Superstor Spool] [Manager] Metric key id 0x1000c9586 illegally used by two metrics: [SuperDomain|Custom Metric Host (Virtual)|Custom Metric Process (Virtual)|Custom Metric Agent (Virtual)Alerts|...] and [SuperDomain/MyDomain|Custom Metric Host (Virtual)|Custom Metric Process (Virtual)|Custom Metric Agent (Virtual)Alerts|... ]; ignoring second.
The same management module .jar file is duplicated in more than one domain directory within the EM_HOME/config/modules hierarchy. In the above example the same jar file was located both in the top level/Superdomain directory (EM_HOME/config/modules) and in the MyDomain sub-directory (EM_HOME/config/modules/MyDomain)
Remove all duplicate management module .jar files from domain directories where they should not be located and restart the Enterprise Manager.
APM 10.5 includes a SmartStor Metadata performance enhancement with more rigorous checking of duplicate metric key ids.