Hi Liwei,

- process instances are suspended but process not locked

Process Instances are suspended either manually in Service Center or automatically after the deployment of a new version the module that contains the process if there are changes that require the process to be suspended (Ex: a activity that was being processes no longer exists or now requires a input that did not exist before)

- processes instances are active, but with error

When activities throw exceptions they will marked with errors. Activities with errors will automatically be retried periodically.

- process is locked

Processes are locked either manually in Service Center or automatically during part the compilation/deployment of a new version of the module that contains the process (automatically unlocked after it finishes).

 - Is there anyway I can throw and handle exception in the process?

Exceptions inside the process should be handled inside the activities. Personally I don't recommend using exceptions to "control the flow" of any logic, if your process needs to behave differently when errors occur, then you should have outputs and Decision activities to represent it in the process.

Regards,
João Rosado

For active process with error, is the frequency of retry configurable?

Hi Han,

Do you feel like the retry frequency is too frequent or too slow?

The retries algorithm has a exponential back-off, so after an error it retries really fast and then starts to delay between retries. 

Also note that as I noted in my previous response "Errors" should not used as a best practice when developing, so having to tweak the retries should not be necessary.
Can you detail a bit your use case?

Regards,
João Rosado