Permission required to Unarchive process

Hi All,

Can any one guide me to use Unarchive process smart service plugin? I just need to know the security permission required to unarchive a process. If i am system administrator, I was able to unarchive process but i am not able to do the same if am having basic user permission. 

Note: I have administrator access to both "Unarchive PM" and target PM(Which i need to unarchive).

Also I was able to use "Archive process" smart service successfully with basic user access.

Please suggest any reason behind this.

Thanks in advance!