Deactivating users in Appian

Which environment are you working on in this case? There are two scenarios I can think of:

• If this is in Development, then deactivating a user could affect scheduled processes. However, the impact here would usually be minor since it's your development environment, so you could check for process errors after the user is deactivated and pretty easily re-publish any process models they created.
• If this is in Production, then you shouldn't have any process models that are last saved by a user account. If following good DevOps practices, you should always deploy as a service account which will not be deactivated, so deactivating any user shouldn't have any effect.

Which environment are you working on in this case? There are two scenarios I can think of:

• If this is in Development, then deactivating a user could affect scheduled processes. However, the impact here would usually be minor since it's your development environment, so you could check for process errors after the user is deactivated and pretty easily re-publish any process models they created.
• If this is in Production, then you shouldn't have any process models that are last saved by a user account. If following good DevOps practices, you should always deploy as a service account which will not be deactivated, so deactivating any user shouldn't have any effect.

I am thinking about development environment. What about the objects that are saved by the person whose user account is going to be deactivated? Will it cause any problem in future??

The only objects that matter are process models, and the only reason those matter is if they are configured to run as whoever designed the process model. Typically anyone working on those processes will republish them anyway once they make changes, so it isn't usually much of a problem.

I have one process model which i have saved recently and its configured to run as whoever designed the process model. When it gets executed, it is showing started by as the previous designer name  in monitoring mode and not my name. We both are system admins for the environment. Any comments on this behaviour Peter??

Did you Save and Publish or just Save? You must publish for it to change the process designer. FWIW I also strongly recommend that you always save and publish because it creates a new major version each time and is easier to troubleshoot / rollback as necessary.

i had saved and published it. I thought my name will pop up but still his name is only coming. Really not sure what I am missing