V$LOG_HISTORY

Data Dictionary View

Columns
   ___________________________
 
   RECID
   STAMP
   THREAD#
   SEQUENCE#
   FIRST_CHANGE#
   FIRST_TIME
   NEXT_CHANGE#

Heres a handy script to list the history of log switches per hour over the last week

Related:

V$LOG 
V$LOGFILE 
V$LOGHIST