I can't find any documentation on it, but it looks like the agent polls ExternalParameters sequentially. Is this correct? If so, is there a way to run them simultaneously (say with some maximum degree of parallelism)?
I have a few external parameters that usually complete pretty quickly, but may sometimes take pretty long. It seems like they're pushing out some of the others....
If your script takes more than 3sec, i would use EXternalParameterProvider.
https://wiki.netxms.org/wiki/ExternalParametersProvider