ASMM Performance Problem

I recently was working with a client that was seeing ASMM automatic tuning causing severe performance problems. They had recently added memory to the SGA by increasing sga_max_size and sga_target. Since Automatic SGA Memory Management was enabled the SGA was continually resizing. This system and application has attributes of both an OLTP and reporting system. Several times during the day the system became unresponsive and we were seeing many pin S wait on X waits and library cache load lock waits. It became apparent that they were caused by the memory resize operations.

Our solution was to modify the interval that Oracle checks and resizes memory to something very high. This parameter is _memory_broker_stat_interval and we set it to 24 hours.