What are the possible causes of premature redo log switching in Oracle other than reaching the specified file size and executing ALTER SYSTEM SWITCH LOGFILE?
We have a situation where some (but not all) of our nodes are prematurely switching redo log files before filling up. This happens every 5 - 15 minutes and the size of the logs in each case vary wildly (from 15% - 100% of the specified size).
This article says that it behaves differently in RAC.
In a parallel server environment, the LGWR process in each instance holds a KK instance lock on its own thread. The id2 field identifies the thread number. This lock is used to trigger forced log switches from remote instances. A log switch is forced whenever the current SCN for a thread falls behind the force SCN recorded in the database entry section of the controlfile. The force SCN is one more than the highest high SCN of any log file reused in any thread.