The SSO integration between NNMi and iSPI for Metrics allows you to change your NNMi passwords without affecting NPS. The NPS does not really have the "system" user defined, this is handled on NNMi. So Metrics you should be fine.
iSPI Traffic uses its own "system" user account. Changing the NNMi's system password does not change Traffic's system password. Again, if SSO is enabled between NNMi and Traffic then when launching the Traffic Master Collector config GUI then you won't need to enter the password (if logged in as system in NNMi). If you want to maintain the same password (not required for SSO) then you can also change your Traffic's system password.
Summary. Changing your NNMi system password should not have any side effects on iSPI Traffic.
P.S: Make sure the "web service" user used during NNMi and Traffic integration IS NOT "system". Otherwise you may experience problems, if you followed the recommendation then you created a specific user for "web services" and then as long as you don't change that password you should be fine.
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