Somehow I kept forgetting this thing frequently enough to expend some effort to write this 🙂
At times when you troubleshooting something in K2 you need to identify process having only process instance ID and frequently knowledge of the solutions and workflow is a missing part (developer is away on vacations or , in the worst case scenario, nobody even knows if there was a developer in the first place 🙂 ). As a sample scenario, you can think of troubleshooting failed process escalation or process instance which stuck in Running state.
Let’s look at this in more details. For failed escalation you will definitely have error in K2 host server log and entry in K2 Server.Async table – that will give you ProcInstID value, and your next steps are: A) Find out which process this instance belongs to and B) Status of this instance. Finding (B), at least if your process is in error state is easy as it supposed to be listed in Error Profiles View where you can retry error and also see Process Instance ID and process name.
But in case your instance not listed in Error Profiles View, or let’s say you going step by step before jumping into Error Profiles, then you still have 2 options to get Process Name process instance ID:
(1) Using Workflow Reporting SmartObjects. You can use Process Instance SmartObject (Workflow Reports > Workflow General > Process Instance) to get list of Process Instances – you just feed ProcInstID to it to get back ProcessSetID:

Process Set ID in turn can be feed to Process Overview SmartObject (Workflow Reports > Workflow General > Process Overview) which will give you Process Name:

(2) Querying K2 database (in case you already in SSMS and too lazy to switch over too K2 Server/Tester Tool 🙂 ). Here is a SQL query you need to run: