To make it easier for operations staff to piece the full log together, certain information is recorded on the last and first lines of LOG data sets that have been swapped.
The first line of a new log that is used in place of a swapped log contains the reason for the swap, or the initiating user ID.
The last message printed on a swapped log is the DD name of the new log. Also printed at the start of the new log is the DD name or logical ID for the previous log.