From my notes:

ANR7837S Internal error LOGSEG871 detected.
        Usually indicates that your Recovery Log is full during server
        restart.  You should have taken architectural steps, per the Admin
        manual, to prevent this; but now it is too late.  You will have to
        allocate more space to your recovery log.  Use dsmfmt to create a new
        recovery log volume; run 'dsmserv extend' specifying the new log;
        restart your server again.