Recovering sessions with cold start

Invalid sequence number mismatches and mismatches where no unilateral decisions have been made often indicate a subsystem restart from an incorrect log or incorrect checkpoint on the log. This situation can require forcing the recovery of the ISC session by cold starting one or both half sessions.

IMS allows authorized terminal operators to change IMS ISC session state from recoverable to cold start when necessary by using the IMS /ASSIGN (subpool to VTAMPOOL) command before attempting to initiate a session. When a session is changed to a cold-start state, the subpool associated with that session is made available for allocation to any ISC cold-startable parallel session with any node.

Session recovery where one or both half sessions are cold started is not considered a major error because, by definition, the cold starting half session has no information from the previous active session with which to negotiate (agree or disagree) recovery or resynchronization.