A Locked Session May Not Opened as View Only Because...
You may want to view a session that you do not own. There are a couple instances when this may not be possible. When a session is sent to the field, it is accompanied by an XML packet. This XML packet stores edits made in the field and must be opened in an Edit mode on the Enterprise in order to play the edits back to the geodatabase.
A session with an XML packet cannot be opened as View Only until its owner has opened it and saved the edits to the database. This is also true if your Administrator has decided to create XML packets on all designs, whether they're sent to the field or not. Once the session's owner has opened and saved it, the session can be opened as View Only by any other user on the Enterprise.
No session may be opened as View Only in the field.
Locked sessions may be unlocked in Session Manager or in ArcFM by selecting the Unlock Session task from the Available Tasks list.
If an Unlock task is not available for a node type, your administrator may need to create it using the Process Framework Administration Tool.