We have a custom NCM Device family that is set using a Real Time search based on the attribute SysObjectID. When the search is set to Real Time no new devices are being added to it. When we change the search from Real Time to Periodic Update (24 hours) it works, what is causing this?
For any Real Time searches you should be careful when selecting which attributes to base the search on as attributes that have an External flag are not good choices.
For SysObjectID there are actually two different attributes
The difference between these two attributes is that 0x117a7 has a Memory flag while 0x10053 does not.
From our Searches recommendation document page it is recommended to use Memory for complex searches as it has the least impact in CPU and time while the External flag is the least effecient.
Verify that 0x117a7 attribute is being used in your search criteria instead of 0x10053.
Having an external flag set, meaning that Spectrum needs to poll the device and wait for a response is extremly costly in searches and would not be recommended to use in a Real Time search.