A user is not able to resolve subcases if the cover case is locked.
According to the below article, Pega already have Product enhancement for this. Will some body help me to find out, Whether this enhancement already have in any pega version or any alternative option to resolve this issue.
This is still not supported. Even if that check box is enabled we still take parent lock while resolving the child.
Instead, you can configure Parent case for optimistic locking. With this, child case worker will be able to resolve the child properly even if someone is working on parent. And parent case worker will just get an option to resubmit.